I'm a Colt fan as well, with a collection of bases. A pleasure to use. I do like the look of the 611, and many folks here like it. To my thinking, the 611's additional half horsepower lets you cut a little deeper per pass. But both take only the smaller shank bits so there's a limit to how big a bit you can use. But man, the small routers are really nice for so many tasks. I doubt you can go wrong with either one. That said, Barb has cussed out her 611 just recently, maybe just a fluke.
The more I do, the less I accomplish.