Honestly its a tough call. The Mustang GT's aren't really that fast, in fact, I would be willing to bet that given a good driver they should run nearly identical. (I have witnessed a couple SRT-4's run sub 14's, one was a 13.9 with a chick driving) The SRT-4 would be cheaper to get a few more hp out of since it has boost. If you live where there is snow, the SRT-4 can be driven year round while the mustang really shouldn't be.
Now on the other hand, if you go with a nice low mileage LS1 camaro thats a different story. (I don't want to hear about them not currently making them anymore because SRT-4's are done too) The LS1 runs low 13's stock and there have been a few that touch 12's bone stock.
All that said, I say go with the SRT-4 even though its a neon. A lot of my opinion is based off the fact that I hate mustangs and they really aren't that fast.
