The LED 3528 strips are older than LED 5050 strips, the LED 3528 is not as bright as LED 5050, but the LED 3528 consumes less energy and produces less heat. If you just need a LED strip, not a super bright LED strip, choose LED 3528. It can meet you needs.
Here is a video to show the differences between LED 5050 and LED 3528 .
LED 3528 and LED 5050
LED 5050 is brighter than 3528
5050 strip is wider than 3528 strip
LED 5050 is bigger than 3528
Get more information about LED 3528 here.