To start with I'd like to say I had the STU for several years whilst swallow and Flight are just about two weeks old so our companionship is not as complex quite yet.
STU (old material)
I always had a good time with the STU - and I think it really could be used for practicing stamina better than the other two sleeves - provided you do follow the instructions for the STU as a stamina training device rather than just pumping away and dumping a load inside. I've been in a long distance relationship for ages so that was the original reason for the first purchase, and I was so surprised the texture - all three to be frank - have something that is better than the real thing. I certainly don't suggest texture can replace the intent and interaction of a partner, but as far as penis stimulation is concerned they all do the trick very well - worth knowing for any future clients who are virgins as we all are in the beginning...
Swallow (Jenna Haze)
First of all - I was amazed by the looks of the mouth - it is extremely well-made and I got not stop myself from playing around with it in a completely non-sexual way before even getting started - you can sort of make it do "faces". It looks like an alien object - it is the cute, pink and fluffy version of something H.R. Giger would have designed - bizzare and fascinating. I am surprised of how blowjob-like the sensation from this sleeve is. Admittedly the sucking and slurping is lacking but the sensation of feeding yourself into a soft mouth and throat is there with some clear similarities to real head. For being canned BJ it is really amazing. Unlike the STU this sleeve does not inspire to retreat practice - it suggest shooting as soon as possible - but it is still much easier to hold back in the Swallow sleeve than in the STU. I firmly believe the STU is better for it's purpose however. It cannot be said too many times - the mouth looks amazing. Worth noticing: penetrating the mouth may need the assistance of a hand as the lips close a bit if you pull out completely.
The new case is the headline here - it has pros and cons. The size is nice - as long as you aren't too long for it - I'm about 7" and still good. The case is much closer to hermetic than the big old normal one. When this is screwed on to a very tight setting there is sincere suction - to the degree that I have seen my cum sucked out of the back vent due to pressure differences after pumping away. As for the texture I am not convinced completely, but then again it is a fairly new toy of mine and it is not bad. For now I am unsure if the quality of the material that is different from the opaque sleeves of mine does more for or against my current verdict - it is at least easier to clean as I see it. I would probably have prefered it to bee a bit tighter - but then I have a quite slim member so the experience may very well be different if you are a man of greater girth. The bottom of the case is not flat but has an angle and it is a bit annoying as it cannot be stood up unless you unscrew the bottom or screw on the top - however - the angle makes it easier to change the suction with one hand only on the fleshlight which is quite handy.
I don't see a reason to grade the sleeves - others have already and I enjoy the variety of experiences I can offer myself and my dick. I can recommend all three and I guess your intentions for buying one may vary. I'd probably not want the Flight to be my only Fleshlight - but it is really breaking new ground with it's case design - over all I believe alternative cases could be the next step to heighten the future experience of all old and new fleshlight sleeves - Flight has really proven difference it can make.
In addition I suggest you don't buy the ID enhancing formula if you aren't allready well stocked with lube - it makes it feel as if you are getting a BJ from a girl with a mouth full of breathmints - and as nice that may be for a change both in real life and with any Fleshlight sleeve - it is not my choice for an everyday experience.
My main advice is: Get a fleshlight - preferably a few...