Well providing the GSI has the C20XE, there isn't much in it. I think the GTE just has the edge though because of being slightly lighter and the GTE can legally go without a cat which frees up about 5-7bhp. GTE 0-60 in 7.4, think the GSI is about 7.6.
But the other GSIs are well off the pace. My mate has a 1.8 GSI and it feels gutless to say the least compared to mine.