Perhaps GTODealer will respond, as he's owned both a GTO and has an SRT-4.
They are both (from what I hear--do not have personal experience with the SRT-4) good cars but are very different types of cars. On one hand you have the small, FWD 4cyl Turbo pocket rocket, on the other hand a larger, heavier, solid RWD V8.
I'll agree with what the others have said on the insurance. Get quotes on both and see how they come out. I wouldn't be surprised if the Goat was cheaper. Or, it might be the same. The only times I've heard of someone having cheap insurance on the SRT-4 was when their insurance company rated it as a regular Neon--in which case they are not likely to get proper payout.
I've heard hit or miss things about Neon quality, but have not heard consistently on how that translates to the SRT-4. Some have said that the SRT-4 is very different in everything, where as others have said that outside the engine and suspension, you still have a not-great interior etc.
This is a matter of personal taste as to which you prefer, but the SRT-4 is generally flashier and may attract more attention than the Goat. Attracting attention includes both regular people and cops.
Try sitting in a GTO (since you have a Neon, I can't imagine the SRT-4 interior feeling much different) and compare seat firmness, pedal layout, elbow room etc.
06 IBM/blue M6 18"