Well, I haven't used a 901, but I have used a Titan, but I am a confirmed Evo and Ecopure fan!
The Titan does have the advantage of having the option of a manual battery, but I prefer my Evo because of the reliability, the battery life, the size (not so much the length, but the width. The Evo is standard cigarette width whereas the Titan is wider, so I'm guessing that as a rollie smoker, you would have found the Titan a MONSTER!), he great flavour it gives, and it's looks.
Yes the carts are smaller, but the Evo is economical with liquid, plus they wick all the way down, so I don't find them a pain at all.
In my experience, yes, a good Titan battery and atomizer will give you a greater hit and vapour, but there isn't the h-u-g-e difference in these two aspects that others seems to think there is. A good Evo will give an average Titan a good run for it's money on these two points (especially loaded with Ecopure).
In any event, I get a greater hit and more vapour from my Evo than I ever did from traditional cigarettes, so I am happy
For general info: I used to smoke either medium or fairly high strength cigarettes - about a pack/pack and a half a day, and I switched completely over to e-cigs the day my Evo arrived.... without intending to! I only intended to cut down on my cigarette use using the e-cig, but it didn't quite work out that way
