Whats the difference between 21xxx and 25xxx ?

I want to buy a PS3 slim that is jailbreakable. And also does not have the nec tokin caps and is more durable..

I know that some 25xxx are jailbrakable and some are not...

Assuming that the 25xxx is jailbreakable, which one should I go for, 21xxx or 25xxx ?

which one is more durable and built better ? 21xxx or 25xxx ?