I would recommend the aircraft. IR requires cockpit organization and the ability to develop an instrument scan. While these can be done in the sim, it's a whole different ball game when you're being bounced around - finding charts, fixes, switchology, the 5 T's, freqs, GPS, etc. You need to experience vertigo and learn to overcome it. I don't know if you can get that in the sim.

Another important factor is the language of IFR. You'll pick it up faster the more you hear it. Better chances of hearing others in the soup as well as yourself (or get a scanner) to get a handle of the clearances, vectors, EFCs, etc.

Good luck - let us know how it goes.