Trying to compare Mac's and PC's is very difficult. There were a couple of mags who did comparisons when the dual g5's came out that showed the high end pcs were still faster. Some would argue the benchmarks are not equal due to code optimizations or whatever, I dont really give a chit about benchies to begin with soI will move on. If you are into that sort of thing, then definately stick with the PC, macs will never touch them. The best thing to do I would say, if you are truely curious, is to sit down with a modern mac and try it out for yourself. I know that may be hard to do, but I was legitamately curious at one time too and that is what it took for me to understand what the price premium and "hype" was all about. Alot of what makes macs so cool, at least for me you cant read about in a magazine. Little intangable things, it sounds like marketing tripe I know but it is what it is.
Also many of the anti-mac responses you will see on threads like these come from people who have never used a mac, so take them with a grain of salt. Im sure you know about people who just need to feel good about what they purchased regardless, so putting down other hardware is the flavor of the day ( Ref any Intel vs AMD, Nvidia vs ATI ad nausium).
Sure there are rabid mac fanbois too, but keep in mind most of them have at least spent quite a bit of time using both platforms. I also know the ex mac users, or the " I used one at work or at school once and .. blah blah blah. I used to be that guy too, untill I sat down with OSX and an open mind but I digress.
Back to your question, I can try to shed some light on performance differrences between the two platforms and what I personally use my computers for. More "generalizations" I am afraid, but if you had any specific cross-platform "free or software I already have" benchmarks you would like to see with the hardware I have, I would be happy to provide them. I honestly dont know of any.
My "game" rig is a 3200 AMD Winchester 64 @ 2600MHZ, 1GB ram running at 260MHZ, 6800GT vid. This is my home computer, I use it to play games and run folding.
My "Work assigned" computer is a P4 2.4GHZ (533mhz I think) and 1gb Memory, I use this for office related apps, word, excel, lotus notes.
My Laptop is a Powerbook G4, 1.25 GHZ w/ 512 MB of ram and a ATI 9600 mob chip w/ 64 mb of ram. I use this for everything else, including the "Work Computer" tasks when I am on the road. I also play WoW on it when I am not at home ( plays very well too )
Basically, seat of the pants performance in regular computing, browsing, mp3 compression, all the "other" sht people do with their PC's I would say the Mac is faster than my P4. but slower than my AMD rig but they are all fairly close. In games, the AMD smokes the powerbook ( duh ). I have never gamed with the P4, but I am sure with a similar video card it would probibly do better as well. That being said, if I could only keep 1 of my computers, even disregarding resale value it would be my powerbook. I just use it more.
I know its not the "specs" you were after, but there it is. Also I would like to add, I did not pay for the apple, so I am not just trying to justify spending close to 3k on a laptop lol. Not trying to diss pc's either so I hope I didnt get any sand in anyones crack, I really like my other two boxes as well and they are not any "less stable" than the mac. Just trying to convey my experiance.
"As far as I can tell the Mac Mini's only real advantage is size. "
For you that might be true, they are not for everyone not going to argue there. For me, its biggest advantage, and why I would choose it over a $500 PC is it will run OSX fast enough. Again, for me that means more than finishing photoshop 3 seconds faster than a $500 PC, but to each is own.