To be honest the insurance is the only hassel, as the S jumps Quite a few groups compaired to the R.
Ok so where talking an extra 22bhp over a standard 98bhp R, thats quite a lot really, but its the way it uses that extra 22bhp which is the thing people like.
If you compair the S to other 1600cc hot hatches its the most powerfull 'Non-Turbo' 1600 in its class - Forget about Cilos and Fiestas as they are bigger engined these days.
A standard S would easier give a Standard Escort RSturbo a good run for it money in my opiuon (not that there are many standard RS's these days)
If your happy with your R at the moment it mite be more cost effective to do an egine swap from 8v to 16v rather than start a fresh with a complete new standard S.