| Cal Poly is supposed to have a good standing in engineering. A big difference between the two is the theoretical vs. practical approach. Being a polytechnic, Cal Poly will give you more hands-on experience from what I've heard. UCI, on the other hand will prepare you better for grad school. If you want to go to grad school, I'd say UCI definitely. Otherwise, it depends on what kind of teaching methodology you prefer.
Nevertheless, given the choice I would go with UCI in a heartbeat. I live really close to Cal Poly and let me tell you... the area sucks! If you're looking for any amount of a college experience, UCI will be a much better choice (even though it is a commuter school). I also know someone that goes to Cal Poly, and the budget crisis really seems to be having a toll on the school right now.
And in general, the UC name is just more well-respected than the CSU name. | 
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