Ogsplash and Geoff are referring to the Oz regs which is supposedly a pans ops reflection, but I must admit I interpret them differently. The wording is from AIP, ENR 1.5 - 2 para 1.3.1 (b):
"where helicopters are operated similarly to aeroplanes, they may be classified as CAT A"
I read the critical word as "may", not must, shall, or will. In otherwords, when doing an instrument approach such as the ILS in the 212, then CAT A is beaut. But in the BK117, when I want to do 120 kias down finals (which, like Nick I also prefer) then I simply use CAT B minima requirements. If I feel I need the CAT A minima (almost never different in Oz to CAT B) then I limit finals speed to 100. I think this is reasonable given the wording that says I "may" operate as CAT A.
As for attitude Vs collective for glideslope, it depends on the machine/situation. Using attitude to correct for glideslope in the 212 can lead to VNE, and using collective to come up at 145kias in the BK can lead to overtorques!! Nick's 4 kts is a good idea, and I'll try it next time - thanks.
In answer to the original question, I think it is easier to shoot an ILS in a helicopter than a fixed wing, and I think from the subsequent discussion you can see that it is far more flexible with far more options.