I'd say stay with the IGP. I guess performance is similar, but the IGP is way newer, so no driver issues, no incompatibilities, no nothing. Plus it uses less power and will result in lower noise levels, even slightly so. If you can overclock it a bit, it's even better. But still, Minecraft and similar games should be ok with it.
I could always be dead wrong as I've never had a 8800GT, but whatever.