Actually, it DOES have the same pots & input jack design as the 620, and IS Japanese. *Differences:
No
neck binding
pearl dots instead of fancy pearl/abalone inlays
ibanez logo isn't a pearl inlay
neck is flatsawn
headstock is black paint, not rosewood face
chrome instead of gold hardware
rosewood fingerboard instead of ebony
different. non flamed finish
That sounds like a lot, but really it's mostly cosmetic. *IMO they sound the same and feel very similar. *The biggies are the fretboard & neck wood cut. *New, I'd probably save my money & get the 420, but I got a great deal on a used 620, so...
Now, the SCA220 IS a very different beast. *Korean made, lesser (and heavier) wood, etc. *Unless you're after a starter guitar, I'd avoid that one.