A friend of mine swore blind that the Spectrum version was just as good as the C64 one, playing it recently it's clear it isn't, however there's something about the limited color base of the Speccy I find quite appealing and timeless. As you mentioned R-Type on Spectrum is a good conversion, which I prefer over the other 8-bit versions. I'm sure there's plenty of videos floating about on YouTube of T2 on Speccy, maybe we can find out there.
Boo! No longplay videos of T2 on spec...a task for somebody perhaps?