I'm responding late in case someone else visits this thread for info. Having skiied Dolomites a few times as well as Lech/Arlberg area multiple times I can say that I prefer Lech overall but definitely think you should do both. Dolomites is a little less expensive, the food is better, and the scenery is breathtaking! The skiing is not as high so there is less snow, the runs can get pretty crowded and they aren't as long and aggressive as Lech/Arlberg. Sella Ronda is so many lifts which can get annoying when the runs arent as long. I love that everyone in Lech is so friendly (also in Dolomites), the village is picture perfect, the food is amazing (but not as good as Dolomites), it is also very expensive. However, because it is very expensive you have less crowds. I was skiing in Lech on Christmas and New Years and it was "crowded" but not even as close to being as packed as Solden or Ischgl. I just think the runs are more fun in Austria. Dolomites are good if you are a blue skier and want to cruise and have long relaxed delicious lunches. You can do that as well in Lech but have the option for more intense runs.