I wouldn't call it a mini killer. I love my Mac mini. But there are some apps that work only on PC and I have a PowerPC Mac mini which stills works very well. I can see getting a Dell "mini" as it looks like it can do its job with PC only software and not take up a lot of space.
If given the choice between one or the other, and I didn't have any computer at the moment, I would still go with Apple. If I wanted to load Windows on it, the Intel processor makes that a possibility and I get the best of both worlds.