In terms of fun, definitely the vtir...

Si being the base model may be a little more "basic" or plain, but would be cheaper insurance.

BUT, once you've experienced the fun that goes with vtec, you may prefer the vtir. also comes with auto climate control and sunroof, carbon fibre interior bits, although that can easily be amended by diy.

i'd suggest take different ones for a test drive, as each to their own