Agree with #2
I have a tilt trailer like #1 and am in the market for an in-line 3 place version of your #2. If those two trailers are your two choices, go with #2.
I haven't had the top freeze shut, but was in MN last week when we got got freezing rain followed by about 10" of snow. That sure didn't brush off with a broom, and with all the weight there was no way to lift the top. Took me about an hour to clear it off. (It was a great example to help convince the wife why I "need" a new trailer, though!)
I also hate it that I can't store much in the trailer. In version #2 you can put a helmet cabinet, shelves, hanging bars, etc. on the wall but you can't do that on version 1 or it will be too heavy or things will fall off when you open the lid. I can tie down storage tubs between the back of the sleds but have to unload it all to get the sleds in or out. (I do have the spare tires strapped down to the front of the top, though.
As said before, the #1 clamshells usually do not have enough clearance height for four wheelers.
Finally, I have often needed to load the trailer by myself. It can be a real pain with the tilt. You either need a snow bank to back the trailer into so you don't have to tilt, or you have to bring extra weight to put on the back of the trailer to hold it down.
As someone else said, the tilt trailer can be fully functional and can work fine. I've pulled mine well over 10,000 miles since I got it in February 2009 with essentially no problems. However, if I had it to do over again and had your two trailers to choose from I'd go with #2 for sure.