I do love my MRC2, especially since I added a riser. But I also run a needle wheel on my FOWLR, and am happy with it (Warner Marine AS200).
A few points for me, I guess, are important...
1. Space. I am not a guy with a "fish room" behind his tank, so space is always at a premium. I like that you can increase the beckett skimmer capacity with height, not width.
2. I like just having one, "unmodified" pump to deal with. Basically, a pump doing what it was supposed to do - pump water.
3. Beckets are super easy to clean. I don't find cleaning of pump impellers as easy. That may be just my setup though.
4. My beckett can pull out a shrimp molt if it makes it through the pump. :)