Hi, we went for Feb half term last year (2010), and it hasn't put us off as we are going again next Feb!
I have only stayed at SL, so I can't comment on other hotels, but we really like it there, and it is great to be able to walk to the parks, as the buses can get quite crowded!
The park stayed open a little later that week when we were there(compared to the weeks either side of the half term holidays), and there was EMH every day. We found that with the early starts, and young children, we were ready to have our evening meal around 6, and then head back to the hotel.
One thing worth noting, the pool at the SL is closed during half term week (we aren't bothered as we found the water too cold last Feb anyway!)
The big price difference is a selling point for us, as we wouldn't be able to take advantage of late park hours anyway, and neither of our children like fireworks!
We took hats scarves etc, and we didn't use them, it was really quite mild, just a small bit of rain but nothing major. But you never know what weather you will get at any time of year, do you?!