Few main differences between IHM and IIHM are:

(1) IHM is a government institution whereas IIHM is a private one.

(2) IHM offers a 3 years degree and also a pg level course. IIHM offers only degree level program. There is no post graduate program offered. IIHM also provides an opportunity to spend 1 years abroad.

(3) Being a government institution, IHM fees is quire less compared to IIHM.

As for the which is better, I again stress on the fact that i do not have adequate knowledge. however looking at their website contents and some internet search IHM (government one) seems to be better positioned.

THANK YOU!