64bit or 32bit
If your system can handle 64bit obviously go with that, if not the. Go with 32bit. 64 is way faster at ripping, the difference between my 08 iMac and 10 Mac Pro is huge. Get 3-4 rips done on my Mac pro to just 1 iMac......no reason to get a Mac Pro, or i7 just for handbreak of course. Just telling you my experience.
I used handbreak on 3 plus hour movies and no more then 2.5
Also a lot depends on viewing. If you do an iPad rip it will be less the 1GB, most of the time, Apple TV is my largest files. So rip for your product, phone, pad, computer, TV, etc. I love hoe handbreak fixed that, since choosing iPad obviously looks better on iPad. AppleTV looks good on my iPad but takes up more space. So just keep that in mind for other uses.