I haven't played a 7621, so I'll just assume the quality is that of a standard japanese Ibanez.
The 7321 has a nice neck, and the binding is well done, however, the tuners seem cheap, and so does the nut. The finish isn't as good as, say, a RG570. It doesn't have that look that you kind of see 'inside' the clear. I don't see a problem swapping PU's.
Anyway, if you live in the USA, ebay is flooded with 7's. I would go with another 7621. If you do not live in the USA, you are like me and kick yourself for not being able to get all those cool cheap guitars
