I do not have experience however I have read today that upstart scripts are fully compatible with sysvinit (legacy) startup scripts

Memory management is a large subject and I think you will need to be more specific.

Some information

32-bits is swiftly vanishing from both the desktop-hardware and Linux software community with evangelists such as "64 studio" leading the way and software houses (adobe, microsoft, apple etc...) following suit.

basically if your pc is 64-bit capable use 64-bits, it's kind of like deciding to have a single or dual carriageway on a road.

*(apologies to guru's who know it's not exactly twice the performance, but it is faster and has a larger infrastructure than 32-bits which is all that matters)