The entry-level cameras from Canon and Nikon both sport a variety of useful features and offer a high-res, APS-C-sized, 24-megapixel sensor. However, the Canon T6i is significantly more expensive -- more than three hundred dollars (at the time of this write-up) -- than the Nikon D3400. If price is your major motivator, you won't need to read much further: both cameras offer excellent performance. The Canon T6i offers a few more advanced features than the Nikon D3400, but in most day-to-day shooting situations, either camera will perform very well.
Both cameras offer a small and light design, with the Nikon D3400 tipping the scales more lightly at 22 ounces compared to the 27 ounces of the T6i. The D3400 achieves its lower price point by sacrificing many design perks -- most notably, a movable LCD screen that's found on the T6i. The T6i takes this one step further by offering touchscreen functionality. The resolution on these screens are comparable -- the T6i has slightly more pixels -- but not so much that you'll mistake either of them for high-resolution displays.
Further, both the D3400 and T6i are geared towards a more simplified shooting experience compared to higher-end cameras, with fewer buttons and controls -- often relying more heavily on automatic settings and menu selections. Both cameras offer a single, primary control dial; the T6i on the top behind the shutter release, and the D3400 on the rear by the thumb grip. More advanced DSLRs often provide both front and rear controls dials, which let you adjust things like aperture and shutter speed independently in manual exposure mode. Changing both aperture and shutter settings on the D3400 and T6i, in manual mode, are therefore a bit more complicated.
Both cameras offer a 24-megapixel sensor, with the ability to create images of 6,000 x 4,000 pixels in JPEG and/or RAW format. The Canon T6i offers 14-bit RAW files, compared to the 12-bit RAW files of the Nikon D3400. While both companies use APS-C sensors in these cameras, they define the dimensions differently: in the Canon T6i, the sensor is physically 22.3mm by 14.9mm in size, while the Nikon D3400 sensor is 23.5mm by 15.6mm. This isn't a huge difference, but when you're packing millions of photo-sensitive pixels into this area, the bigger, the better.
This slight size advantage is backed up by the DXOMark performance for the cameras: the D3400 offers better ISO performance and a higher dynamic range. Without delving too much into the DXOMark test results, this just means that the Nikon D3400 is slightly better at providing images that don't have as much digital graininess in low-light situations (all things being equal). The D3400 is also able to more faithfully capture scenes, which have areas of both bright and dark areas.
Both cameras offer a shooting speed of five frames per second, or thereabouts, but there are a few important differences beyond that. The Canon T6i offers a much better mirror mechanism: the viewfinder blackout time is only 0.09 seconds (this is the time that you won't see anything in the viewfinder while the camera takes the photo). Compared to the 0.2 seconds of the D3400, it's not a huge difference, but it's probably enough that you'll notice it.
The number of photographs each camera can take before the buffer fills up and it has to take a break to write out the data is slightly different. The T6i can take a mere six photographs in RAW mode before its buffer is filled, whereas the D3400 can take 12. However, in JPEG shooting mode, the T6i can shoot until the cows come home, never needing a break, while the D3400 can only shoot 100 photographs before its buffer needs a break.
The T6i offers a much more advanced autofocus system than the D3400. In the T6i, there are 19 cross-type AF sensors, which provide excellent performance when focusing upon and tracking subjects. In the D3400, there is only one cross-type AF sensor (in the center) and ten regular AF sensors -- it's no slouch, though, and will probably perform satisfactorily in most situations, but Canon has just invested a bit more heavily in this area than has Nikon.
While both cameras offer a similar 24-megapixel resolution, Nikon has elected to go without an Optical Low-Pass Filter (OLPF) on the sensor. An OLPF has been used traditionally to soften the image slightly thereby reducing the occurrence of unsightly moiré and aliasing artifacts. The positive tradeoff by forgoing the OLPF is sharper, more detailed images, especially when the camera is used at its lower ISO settings. As ISO is increased, this sharpness is hampered by increased noise, so generally, this advantage is only present when you use lower ISO speeds.
Otherwise, both cameras offer very good image quality with excellent options for fine-tuning contrast, saturation, and hue.
Of the two cameras, the Canon T6i offers better options for connectivity, including NFC (near field communication) and Wi-Fi connections, while the Nikon D3400 offers only Bluetooth. If getting your photos off your camera without a wire is important to you, the T6i will be faster in this regard. However, this comes at a cost: battery life. Bluetooth uses much less power than Wi-Fi, even if it's not as fast.
The bottom line on battery life is that you'll want to stock up on extra batteries if you're taking the Canon T6i out for the day: under standardized CIPA testing, the Canon T6i can manage approximately 440 shots on a fully-charged battery, compared to a much greater 1,200 shots with the fully-charged Nikon D3400.
The Canon T6i offers a few other advancements that aren't present in the Nikon D3400, probably reflecting its higher price point: the T6i includes a port to attach an external microphone, and its live view system offers on-sensor phase-detect autofocus (meaning, it will focus more quickly and more accurately in Live View mode, compared to the Nikon D3400). Lastly, the pop-up flash on the Canon T6i is slightly more powerful than the one found on the Nikon D3400, offering a guide number of 12 compared to the Nikon's 7.
Both the Canon T6i and the Nikon D3400 are extremely capable cameras, offering a wide array of features. The Nikon offers a simpler, less expensive shooting experience compared to the Canon, but in everyday situations, both cameras will get the job done admirably. The only other factor that might be worth considering is that the Nikon D3400 was introduced a bit more recently than the Canon T6i, meaning that it will probably be supported by Nikon for a bit longer, before a new model comes out to replace it. With the Canon T6i, it has already been succeeded by the newer, and more expensive, Canon T7i.
Maximum effective ISO is an estimate of the highest sensitivity at which a camera can capture excellent quality photos.
Cameras with higher effective ISO will be better choices for indoor photography, night shooting, and indoor sports photography, especially if you intend to make large prints.
You can learn more at our glossary entry.
Maximum effective ISO test data courtesy of DxO Mark.D3400 test data on DxO Mark T6i test data on DxO Mark
Cameras with more dynamic range allow you to take photos with dramatic differences in highlight and shadow areas while retaining detail in both.
Think of a brilliant sunset on a rocky beach: Bright sunset in the background, with dark rocks in the foreground. High dynamic range means more of the extremes will be faithfully reproduced.
Dynamic range test data courtesy of DxO Mark.D3400 test data on DxO Mark T6i test data on DxO Mark
Cameras with longer battery life can take more photos before exhausting their batteries.
Special note: The measurement standard for battery life stipulates that if a camera has an internal flash, it must be used for 50% of photos taken. For this reason, comparisons of one camera with an internal flash to another without will not be comparable
Highest resolution Canon APS-C camera yet; Improved dynamic range over T5i; Good high ISO performance for its class; Very fast autofocus; Built-in Wi-Fi with NFC; Touchscreen tilt/swivel LCD.
Shallow buffer depth with RAW files; Below average battery life; No Servo AF in Live View; No 60p video frame rate.
Compact DSLR camera body; Excellent image quality; Reliable single-shot autofocus; Good continuous JPEG shooting performance; New kit lens has improved AF; Great value at current prices.
SnapBridge is slow and limited; Poor continuous autofocus; No built-in Wi-Fi; Mediocre video features.