I think aircraft time and sim (Frasca) time are complementary. The sim is particularly valuable early on during the IR training when you are getting the scan together and making a muck-up of some of the approaches. A good sim instructor can pause the sim, explain where you are going wrong, and restart the sim either from the freeze point, or from an earlier part of the approach.. .This provides a faster rate of learning than flying real approaches where traffic often limits you to a couple of approaches per flight.
However, there comes a point where you need to move onto the aircraft to progress. It can then be useful to go back to the sim for a session if there is something you are having particular trouble with.
The most important thing in IR training (after the funds) is the instructor and this applies to the sim instructor too.
Just a tip.... When you are part way through the IR training, it seems impossible to fit in all the tasks, talk on the radio, calculate airways join times, and fly the aircraft to the required accuracy while still finding time to fit in all the checks. Everyone with an IR I have talked to has felt part-way through the training that it was beyond them and wondered what they were doing on the course, spending money faster than a playboy. Keep your nerve, work hard, and it eventually comes.
I was lifted from the depths of depression by a poem that appeared in the wannabee section of pprune. If I can find it I'll post it here. It worked for me.
Finally, good luck !