First off, let me preface this by saying I am no 'expert' in higher voltage PVs, having just started using them in the last week and a half. Until then I was using my 510s mostly, M401 Dragon as my go-to after that, and the others in my sig off and on for the last 2 months.
My first experience was the Jantystick at 3.7v. I hated it only due to the terrible inconsistency in that unit (not a reflection on all 3.7v PVs), and the 801 mouthpiece.
I could not decide between the vast number of hot-rods available, so I pinged Zofryer since he owns almost all of them. He said that at the time, his Prodigy was his main vape. Many say the same thing. The reason is the 5v performance. It is the only 5v hot-rod out there (although there are some handbuilt mods made of flashlights some users have made) and the draw to it is the flavor. As I understand it, 6v for some people 'burns the flavor' a bit for their liking.
Once my Prodigy arrived, I have not really touched my e-cigs, not even my 510. The flavor is worlds better with the same juices I normally vape, the battery life is beyond compare, and the vapor production is terrific.
I bought my VAPRE51 to be a more portable device to replace the Jantystick. It will not produce as much vapor and not nearly as much flavor as the Prodigy, but it should pacify me in the instances that I cannot carry my Prodigy.
I bought the SB v1.1 because it is GORGEOUS, and vapes at 6v. I can also take it down to 3.7 if I choose to. I have yet to hear any bad reports on the SB.
I was unaware of the Chuck and Little Chuck when I bought my others. I surely would have bought one... they rock and can be made to order in custom designs. Not as "slick" as the others listed above, but they work well.
If what you want is as small as possible, I say go for a VAPRE51 or VP1. Good 3.7v performance, looks cool and performs on the level of the Jantystick without the inconsistency. If you want to go one size up and get even better batt life, do the VP2.
One step up in size with a good reputation is the Screwdriver. Still 3.7v.
If you want to go for 6v performance (more vapor, more flavor, but might be too harsh of a throat hit for some) the options I listed above are all killer, but going back to size... the Super T1 is the winner. Amazing craftsmanship, ingenious design and execution, and very, very slim and compact.
I will be buying a Super T very soon, probably on his next batch.
So IMO (again, this is my opinion, and not based on trying everything out there)...
3.7:
Little Chuck for lower budget
Silver Bullet or VAPRE51 for cool factor
Each should perform equally
5v:
Prodigy. It stands alone here, but keep in mind the Prodigy will give the best possible flavor
6v:
LOTSA great choices.
Super T is my top pick
SB v1.1 next best
Any others sure to satisfy
I cannot comment on the Protege since none have been produced yet. Basing on the performance of the Prodigy, I can imagine it will be superb.
There are others more qualified to help you make your decision though. Perhaps in a couple months I will be too
