I'm pretty sure that Engine Ice is just Propylene Glycol based, whereas the recommended antifreeze is Ethylene Glycol based.
The Propylene Glycol has a slightly higher heat capacity, but is more viscous, so it will work your water pump harder. I think that this whole area is another area where vendor obfuscation of what's important is rampant. Either one will work. PG is probably a bit less toxic to the environment.
Triumph's recommendation is for an EG based product. I don't think it matters which you use ... but for my money, I'll just buy the coolant at a local motorcycle dealership. And if I didn't live near a dealer, I'd just go to Walmart and buy a 50-50 EG ready to use mix.
Edit: I just looked at the Engine Ice web site and in the FAQs they identify it as PG. They also go on a fairly unwarranted diatribe about the evils of EG and the wonders of PG.
This company is just selling something "different," shrouding it in difficult to expel mystery, and bad mouthing their competition.
I reiterate ... you can use either one. PG won't hurt anything. But it is not some magic wonder fluid that is worth seeking out. It's just something else to sell.