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.SL2 test data on DxO Mark 7D Mark II test data on DxO Mark
Excellent image quality; High ISO performance improved over predecessor; Excellent burst speeds (up to 10fps); Significantly improved buffer depths; 65-pt AF system; Dual Pixel CMOS AF; Can focus down to f/8 (great for teleconverters); 1080/60p video; Headphone and mic jacks; Rugged build quality.
Autofocus speed (AF shutter lag) slower than 7D and 70D; Mediocre battery life for a pro DSLR; Dynamic range at low to moderate ISOs not as good as competitors; Phase-detect AF did not perform as well as expected in our low-light AF tests; No built-in Wi-Fi; No autofocus for 1080/60p video.
Higher resolution and better image quality than SL1; Much improved dynamic range; Excellent Dual Pixel CMOS AF; Compact body with improved ergonomics; Articulating touchscreen; Full HD movies up to 60p; Better battery life.
Shallow buffer depth with RAW files; Dynamic range and high ISO performance still not as good as leading competitors; No 4K video option; OVF only offers 9 AF points.