The one thing I realy don't like about the Scorpion is that the switch can get accidently turned on in a pocket fairly easily. It has a higher light output than the UK2L, and has an adjustible beam. It's also significantly larger, if you want to carry it in a pants pocket. For a jacket pocket, it probably doesn't matter.
The UK2L is smaller, costs less, has significantly longer burn time (3 to 4 hr, vs. 1 hr for the Scorpion). It also is very unlikely to get turned on accidently in your pants pocket, since you have to twist the head to turn it on.
I've carried the same UK2L in my left front pants pocket for around 8 years now. I've *never* pulled it out and found it dead in my pocket, and it seems to give a fair amount of warning when the batteries are on their way out, too. It's the one flashlight I *always* have with me.
So it depends a bit on what you want to use the light for; but for continuous carry, I don't think you can do better than the UK2L.
I seldom use my Scorpion anymore; the SureFire E2 does the same job much better, IMHO, but I wouldn't want to carry one in my
pants pocket all of the time. I'd go through 3 or 4 times as many 123's, if nothing else. And I hate to think what an E2 would look like after several years in my pants pocket. The UK2L is cheap enough, if I trash it, I wouldn't get too upset. Not so for the SureFire E2.