My daily carry is an E2. I would buy it over a G2 anytime for the clip and the smaller diameter. In my smaller hands, the E2 is actually easier to use the Rodger's technique because of the smaller diameter and the more agressive checkering than my 6P. 'course that doesn't matter much since I have a P111 on the Glock
I can't comment on the Pelican Stealthlite or the UKE 2L since I haven't used them. I do own a Scorpion, though. I carried it in my bag for awhile, but since I got the E2, it's stayed at home.
Before I get into the merits of the Scorpion, I'd like to point out that if you plan to use your light more than a few minutes per day, then any of the high power lithium lights are not good economy. Even at a 75 minute run time, I don't use the E2 for everything if I have an alternative that uses rechargeables or a cheaper battery. Personally, I use an LED light unless I need the high intensity. If I wanted a higher intensity, I'd buy a Stinger or 8NX/AX or 9AN. I have a 6R that sits on the nightstand because I don't carry it around with me.
Although I think that Surefires have better beam quality, I prefer the Scorpion for non-tactical work. I like to be able to widen the beam for lighting up an area within 10-20 feet. Also, within 5 feet, a widely dispered beam is more useful. I haven't used mine enough to wear out the switch, so I haven't had any problems with it. I find that it's easier to use one-handed than twisting the end of the 6P (the E2 is easier, but still not as easy as the Scorpion). The Scorpion is also not so expensive that you cry about beating it up. (I thought that I had lost my E2 on the subway a few days ago and almost cried at the though of being without it until a replacement arrived...however, it turned up clipped to a thread on my lab coat.)
If you think that you will be in a tactical situation, the Surefires are the way to go. A few months ago, before I had the E2, I was carrying the Scorpion. At an incident where my blood was pumping, I wanted to light up the target with the momentary switch but ended up mashing the switch to click it "on" instead. Had I been carrying the E2 or the 6P, the light would have been off when I wanted, and the beam would have been focused more intensely on the target.
Bottom line:
for non-tactical work, a Scorpion or a Stinger
for possible tactical situations; an 8AX/NX/9AN or an E2 (or M2)
gm