I *owned* (past tense explained soon) all of them so here's my experience with them:
Very good, and yet not a lot to it, which is probably a good thing. Quick and easy to reload (I love the little switch press to load the disk in; its a nice touch :3), gets long ranges, as well as being comfortable and light.
The only main drawback is it's bulkiness; for a single shooter it is awkward to try to holster or carry around.
I found the Proton to have more range than the Vigilon and about the same as the Praxis ... but that just could be *my* blasters.
My preferred 'sidearm' rather than the proton. Sure it's big and bulky, but similar to a Recon/Maverick love child.
Reloading time is average (since sometimes it can be a bit fiddly trying to stack the disks ontop of each other in the built-in clip) but the rate of fire is excellent and is what really makes it worth carrying a Vigilon around.
PROTIP: You can actually fit 7 disks in without jamming it. You load six disks in, prime it so it loads a disk onto the launch sled, then fit another disk in. +2 more than what the Nerf recommendation is, and no modding required!
My favourite of the current Vortex range. It's essentially a magazine-fed, pump action shotgun... who WOULDN'T want one?
Despite the Vortex range being generally clunky in size, the Praxis actually feels the most justified considering the pump action grip, being magazine fed and can take a shoulder stock attachment, plus being designed as a 'rifle'-esque size, not with a "as small as possible" restriction.
Be careful though; I've actually bought two Praxis' with manufacturing problems, and online it seems to be a common case. My first one kept dropping the magazine out if I pulled the trigger too quickly, especially when the pump action grip hadn't fully returned yet. My second Praxis had the issue of not accepting the Nitron 20 magazine... but I took out the long post with a spring on it and now it works fine, so mild modding required. I didn't take either back since now I have one that DOES work, and the other for spare parts. Despite this, definitely going to be my primary during indoor / close quarters wars.
PROTIP: You can do the same kind of trick as the Vigilon; load 10 disks into the clip, prime it so it loads one onto the launch sled, then pull out the magazine and refill with another disk. Voila; 11 shots ready to go.
Just don't. Seriously the worst Vortex, below-average flywheel blaster, and not really worth modding from what I've seen. The only reason why you SHOULD buy one (cheap if you can) is for the 20 disk clip for your much more superior Praxis.
Before badgering on about the Nitron's flaws, the 20 disk clip is insanely helpful for the Praxis. LordDraconical on YouTube said he finds it 'a bit long and clunky' but I find it doesn't get in the way at all... unless you've got big arms and holding it wrong.
It's huge, the front grip isn't detachable and for some people can feel awkward (so-so for me personally, my friends hate it) and it's just too loooooooong. The weight isn't actually too bad, but obviously better once done a battery mod.
The Nitron shoots about a similar range as the Praxis, but here's the big drawback list for me: the speed it fires the disks at is slow, the rate of fire is too slow for a battery operated Nerf, but worst of all, the REACTION SPEED is terrible! It takes me half a second from pulling the trigger (after the flywheels are fully spinning) to the gun actually pushing the disk into position, then another fraction of a second for the flywheels to actually grip and spit the disk out. Not impressed. It seems the voltage mod helps this... *a bit*... still not all that impressed considering all the other drawbacks.
The scope is a bit hit-and-miss...looks awesome, but isn't really all that functional. In bright daylight you can't see the lights much, in darkness you ONLY see the lights xD I'll probably chop this one up and turn it into some other type of scope or aesthetic mod.
Reason why I said *owned* (past tense) at the start is I've given my brother the Proton since he liked it a lot, and I tend to use the Vigilon instead, but also due to how awesome the Praxis is I've actually disowned the Nitron that it's that bad ... definitely either going to be chopped up for future potential modding projects, or maybe even sell it to someone who doesn't need the ammo clip or the scope...
In summation, I find the Vortex 'tech' to be very cool. The long ranges are fun, the only drawback being they travel slower the longer they drift, but are still accurate and fast at close-mid ranges. Very satisfying to ricochet off walls and curve around corners. Out of the current Vortex range, the Vigilon being quite flexible and the Praxis being the most powerful, I think Nerf have done a *good* job. I wouldn't say ground-breaking in that dart blasters are still my preferred armoury choice, the Proton would have been nice a little smaller if it was possible, and the Nitron does not deserve to be called the 'flagship' Vortex model.
Hope this helps anyone make a judgement on these Vortex blasters