0918,
The main difference I can see (see my LASORS post above) is that you can cut out 10 hours of CPL intrument training. But then you have to do the multi before hand. Notwithstanding the major task of taking full control of your training and getting the FTO to do it your way.
I cannot see Keygrip's original point that it saves 55 hours of hour building and the inference that it is as such, substantially cheaper.
I guess your best bet is to talk to the dedicated IR providers such as Bristol Flight Training and see what they think.