I own both systems (all 3 actually), so I feel I can give a fairly unbiased opinion. You need to ask yourself the following questions:
- Will I be playing mostly locally by myself or with family/friends who come over to the house or will I play mostly online via co-op?
- Do I care about more gamerscore points?
- What do my online/offline friends have?
That being said, I've opted for the 360 version of both RB1 and RB2. Xbox Live is so much more fleshed out than Sony's service (get HOME up and running soon already!), and even though 99% of my playing is at home alone or with my wife/kids, I like the option of just jumping in no problems. Almost all the people on my friends list on XBL have RB1 or 2 so that helps as well. I don't care so much about my gamerscore per se, but all else being equal, it is a nice perk.