I just went through the same decision. In the end, I decided on a Laser II because I wanted to be able to practice with as many sails as possible. I posted in forums and asked around, and was told that I should be able to single-hand the Laser II. (That said, I've only been out on it with friends so far, so I haven't tried single-handing it yet.)
One thing to consider: my Laser II was in poor shape when I got it, and while working on it, I found that parts are getting harder to come by, since the Laser II is no longer being made. There are quite a few parts that are identical on a Laser, so you can order those, but others are a little more iffy. For example, mine came without a spinnaker, which I figured was no big deal - I'd just pick one up somewhere else. But I've been surprised by how difficult it is to locate a whisker pole for a Laser II.
Overall, I still think I made the right decision - it's fun to have two people out, I should be able to single-hand, and I get to practice with both the main and jib (and spinnaker, if I can ever find one.) But there are drawbacks to be aware of, such as limited racing and parts availability.
Melges M20 - The Can-Do Girl
Lake Perry, KS