You really have to ask yourself what kind of wheeling you're going to be doing. Out here in the midwest, we have tons of mud so I decided to go with the RE12000. Worm drive winches are super slow, but are generally more reliable than the planetary winches. However, I was just in Moab and I think I winched about 4 times, and I think they were all on Metal Masher (approach to widow maker, widow maker, rock chucker, and some new extra credit obstacle). Here is a pic of the approach to widow maker....
http://www.pbase.com/ruppsrover/image/42159561
We all used the winch here to just put pressure on the front of the truck from the opposite angle we were leaning. To the left of my truck is about a 40' drop straight down. I don't think you can see in the pic but the front left tire is climbing while the front right tire is dropping into a nice little hole. There were a few rocks up there but after Marc pushed them out of the way and slid to the right, we just decided to hook up the winch. In this situation the RE and my brother's MM worked out perfect. The slow winches gave us great control on the speed. Not that Marc's EP9 didn't do a fine job either, but didn't have the same control. Here's a pic of widow maker....
Now in this situation I wish I had a planetary winch for the speed. I was sitting there spinning the tires trying to help out the winch but was only going as fast as it would pull. Marc flew up this once his tires got past that hump, and was able to continue up the hill at a nice pace while spooling up the winch. I had Marc pull my rope to the side while i drove up. Then I coiled it up around my a-bar at the top of the hill like this...
The next obstacle Marc and I winched at is rock chucker.....
On this obstacle, I got up the first ledge no problem and got my front on the second ledge but because I didn't have room to really bump it up the second ledge, I kept pulling myself to the right into a small hole. I had about 6" before my right rear tire ended up in that hole which would have definately made me turf. This is another situation where I just needed a little nudge to get the rear tires in a spot that i could just bump it up the rest of the way. Marc and I had identical lines. He gave the winch a little nudge and was able to get up mostly on his own power. Finally I winched on an extra credit obstacle yet on the same trail.....
In this situation, the soft soil caused my left rear tire to dig a nice hole at the base of about a 3' ledge. The back of the truck stayed stationary while the front of the truck pulled to the left. You can see the drop off to the right of me. It wasn't a spot that I wanted to end up in so again i hooked up the winch and performed a nice controlled pull. This was a situation where the RE performed well. So for my type of wheeling, the RE is the choice for me. While slow up the some obstacles, it still got me up and didn't smoke doing it. I'm sure I'll be making some long pulls in the mud out here this summer, and I'm sure the RE will do fine.
So, if I was only wheeling in Moab I would probably go with a planetary winch. But for general winching situations, I would have to say go with a worm gear.
*here are all of our pics of Metal Masher if anybody is interested:
http://www.pbase.com/ruppsrover/metalmasher&page=all