Howdy I know prowling mastery is really awesome from what i have heard but how does invisibility stand up to it? Ive beaten the game about 3.5 times and I never really messed with either.
I don't know the answer for your question, having never used invisiblity. As the self-appointed welcomer, I just wanted to say "Welcome to the Forum"! :wavey:
Prowling sucks. I have used invisibility and prowling and to me neither are worth it, but if I have to choose it would depend. Either for a magic or a neutral character and prowling for a tech character.
As previously stated depends on your characters bias. But I would have to say invisibility. I was playing around with it some and you could literally run into monsters and they don't notice you. Seems even with master prowling if you got within a few squares they would notice you. Haven't tried invisibility in combat though. Master Prowling in combat with firearms is ridiculous. You can stand 10 tiles or less away in broad daylight and just gun down your enemies without them even noticing your around. Its a game ruiner in my opinion.
Then go for prowling. Most thieves go for tech anyway. In which case it would be harder to cast spells. Besides all of the previous spells in the college would be useless.