I agree that the more realistic the better. The main reason I chose Atlantic Flight Training for the IR last year (apart from the obvious geographic proximity) is that they do the sim part on an FNPT II with visuals etc. OK, it's meant to be IFR, but it helps for cloudbreak, and the airports are not generic - they actually represent Coventry, Leeds, etc.
I couldn't have imagined doing the IR on a Frasca 141. Another added bonus with an FNPT II is that the CAA allows up to 35 hrs. (out of 50) to be done on the sim before transition to the "real thing" (Cessna-310 in my case), so lowering the overall cost of an IR.