I would normally not recommend the Mac Mini for "heavy" video editing either. The Mini uses "laptop components" so tends to have lower overall thoughput compared to an iMac or Mac Pro. This also means that a Macbook Pro (or Air) will likely have slightly less performance than a iMac and Pro as well.
...Do you believe the CPU or GPU is more important speed wise when it comes to adding many effects to video clips?
My past experience lends me to believe that it's a little of both, with more CPU than GPU. But a lot depends on what you're doing. Realistically, a 0.1 0.2 GHz difference in CPU or GPU speeds is not so important. But more complex effects often needs more RAM. You may want to consider getting 16GB at a later date. (Apple has a max of 8GB, of vendors like OWC have tested the current Minis to 16GB of RAM.) Again, it depends on what you're doing.
Mac Mini: 2.7GHz dual-core Intel Core i7 with AMD Radeon HD 6630M
or
Mac Mini Server: 2.0GHz quad-core Intel Core i7 with Intel HD Graphics 3000
That said, do NOT get the one with the Intel graphics. That is not a separate dedicated video card like the Radeon, and uses "shared memory" rather than dedicated memory for the video. It's much better than "integrated graphics" of past Minis, but not as good as the Radeon.
And if you can afford it, get the 7200 RPM drive to partially compensate for the thoughput issue I mentioned previously.