I don't really think the stability is something to question.. as each versions seems to be equally as stable (depending on system specs of course
) but I agree that you should go with 64 bit version as it does allow you to use as much ram as you can throw at it..
And it is more beneficial with some apps.. as in they run faster (the native 64 bit one's that is, and some have reported that some 32 bit apps run up to 25% faster too in a 64 bit atmosphere)... The only thing you may run into is driver trouble.. where your laptop is 3 yrs old you may have to hunt around for some of the drivers but I'm sure you'll be able to find one's that will work none the less... So yeah, 64 bit would be a good choice..