When I first received my X, I immediately installed LP due to everyone's suggestions on this forum and the negative reception MotoBlur received. Unfortunately the first device I received was populated with dead pixels, so I only had the phone for about two weeks before I received a new device.
With the second device, I decided it would give me an excuse to try ADW. I actually used this for several weeks, finding not only the ease of applying themes great, but the fact that it ran flawlessly on the X. I also enjoyed the ability to resize widgets, which at the time LP could not do.
Than of course LPP (extra P is for "Plus" - paid version) came along, and with it brought a whole new game to the launcher market. With the promise of constant updates by the developer, and with such a low price, I figured I would give LP a second chance. I'm glad I did, because ever since than I've only stuck with LPP. And as promised, the updates have been constant (specifically in the area of self-made widgets). The only thing I'm not a fan of, is the fact that every now and again, the launcher tends to become a bit sluggish for me, specifically when I awake the screen.
I'd say your best bet is to try out both (LPP unfortunately cannot be returned before 24hrs of usage because it's not "officially" on the market) and see which ones cater to your preference.
Either way, you can't go wrong with either one.