Would it make a difference if the adata ssd was 256 and the evo was 120? (In speed of couse.) I found the adata one for only about 170.
Slightly, maybe. Larger drives, of the same model line, are generally a teeny bit faster. Again, not that you'd actually notice in real world use.
Read here and make your choice:http://www.tomshardware.com/reviews/ssd-recommendation-benchmark,3269.html