The Airfix Vosper MTB represents a different version (a later type, I think) to the Revell one -
the cabin/superstructure and armament configuration are totally different.
Regarding the kit quality, it's definitely much better than the Revell
kit in terms of moulding quality and fineness of detail (it dates from
the late 70s I think, whilst Revell's Vosper is a 60s mould), but I
can't really comment on accuracy. It looks OK to me but I'm neither an
accuracy nut nor an expert on Vosper torpedo boats (or any ships/boats
for that matter!). I do know that Airfix's German E-boat (Schnellboot
S-7) is supposed to have some inaccuracies as regards the hull shape.
If you had to choose between the two, I'd definitely advise going for
the Airfix kit, but they're such different boats that if you're a fan
of 1/72 scale naval models, it's worth building both.
I have the Airfix Vosper in my kit stash (built the Revell one last year). Would photographs of the sprues/parts be of any use?