I am in the relatively rare position of having both, so let me throw in my 2 cents - and $2K+.
The mini I have is exactly the one you described - 1GB/100GB duo. Picked it up at the Apple Store in NH today after returning a stock duo I'd bought but not opened Wednesday.
The 17" Intellimac I have is the stock 17" which I've upgraded to 2GB.
I have many, many hours of Intellimac experience, but only a couple so far with the mini.
The Intellimac I have because I'd gotten one of the Developer Transition Kits that Apple allowed us to return early for a "free" iMac (well, we paid $999 to loan out the DTK and $500 or more to be in the developer program, but still...).
The mini I purchased for use in my family room, soon to be accompanied - hopefully - by a 37" Westinghouse 1920x1080 TV (the perfect size for my small family room). I hope to share video with it, check email at times, etc. Also, I will bring it to work occasionally - my company buys only PCs and the mini is a
relatively inexpensive and small option to bring in with me.
After a few hours with the mini, my strong recommendation to you is to buy the
iMac unless you need the size of the mini. I love the mini - I
love the mini - but primarily because of its size and because - for the family room - the monitor is not only unnecessary but would be distracting.
My reasons to recommend the iMac are the following:
- The graphics on the iMac are clearly superior. That's not to say the mini is bad - it is much better than I had expected given all the whining. The mini does fine with graphics, not so much 3D, but generally it is quite good. The iMac is just simply a lot better.
- I have a 20" Dell connected to the iMac - it spans natively, works great, and gives you a 2-monitor option which the mini simply won't allow.
- The iMac is a bit faster. Overall, not really noticeably so, but a wee bit.
- The iMac, sans 2nd monitor, looks a lot better than the mini connected to a black 3rd party monitor (very minor point).
I love both of them, but they clearly serve different needs and have different plusses and minuses. If you are not certain, I can assure you that you'll love either choice, and you should just pick one with no backward glances. But, if it were me and if I could afford either and if space were not an issue, I'd pick the iMac.
FWIW, I bought an iLugger case, making the iMac effectively portable, but it'll never be as easy to lug as a mini.