Obviously if you constantly drain you battery fully it will reduce the battery life of a pax or an inhalater. But assuming you treat both properly, then the XP will have much better battery life.
I chose the XP over the PAX for the following reasons:
1. The PAX is notorious for wasting bud.
2. The PAX has all its stealth lost if it is unclean. The smell is awful unless you clean it daily.
3. The XP has longer battery life, can be used during charge, and is more portable because you can use any microusb charger, which are everywhere.
4. The PAX has shit modes to choose from when vaping. You either get, no vapor, shit clouds, or burnt weed. Definitely an overstatement, but I really didn't enjoy the 3 setting only on the PAX.
5. The XP to me is more about performance (thick clouds, good battery, etc) where the PAX is more about the looks. It was an easy choice for me. Just like picking my android and HP computer over any apple products. It may look nice, but in a performance test it gets beat all the time.
As far as the other vapes you mentioned, I don't know enough about the pro to comment. But I did alot of research on the ascent as well, and its just like the inhalater was about a year ago. Great on paper, but just has way to many QC issues. The ascent may very well be better than the XP if it works, but right now it doesnt work and its just a huge hassle. If you want the ascent, definitely wait before you get it. I would have said the same about the XP a while back, but now its kind of at the point where everything is starting to kick into gear.
All that aside, the only real advantage the ascent offers over the XP is digital temps and glass on glass connection. It will taste better most likely, but the digitial temperature range accuracy will probably be questionable even when they get everything working. I've never found any digital units to be accurate with temperatures, because once you draw the temperature decreases rather quickly.
If you want advice on picking the right vaporizer for you, you need to come up with a list of your priorities. Like if your only priority is taste, then I'd recommend the solo and or waiting for the ascent. Although if you just want a good overall portable, the best on the market right now is probably the XP. The solo is great too, and cheaper, but not truly "portable" like the XP.