I played through Case Zero on the 360, and I'm tempted to get Dead Rising 2 for PC. It's cheaper and will look nicer. But I'm afraid that I'll be missing out on some super combo weapon or story content that is exclusive to Case Zero owners. If it's just the five levels, I don't care.
What exactly does importing your Case Zero guy into DR2 get you?
Combo Cards. A few pieces of clothing get unlocked at the safehouse seemingly independent of what you actually wore in case 0. PP and level cap at 80,000 and 5. Scratch cards also carry over, though this is of dubious value. Money carries over, but being easy to come by in fortune city, this isn't much benefit. Mostly, you're getting to start at lv 5, and the only really big thing is the card you get from killing case 0's psychopath. Normally, you would have to reach a fairly high level to unlock the boomstick combo card.