I think I will upgrade eventually but not straight away.
Problem is I keep seeing iMac 2011 quad core i5s going on ebay for around £640 which is cheaper than a mini!
Sam.
Maybe this will help you make up your mind. I did some research with the help of a friend and found the following information.
Turns out the Mac Mini's processor outperforms all the 2011 iMac's, 21.5 in or 27 in. The 2.6ghz quad-core i7 in the new mac mini is the same 2.6ghz processor used in the new macbook pro retinas.
2.6ghz i7 (2012 mac mini/macbookpro)
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i7-3720QM+%40+2.60GHz&id=895
These are the benchmarks for the three 21.5 in. iMacs (mid 2011):
2.5ghz i5
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i5-2400S+%40+2.50GHz&id=794
2.7ghz i5
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i5-2500S+%40+2.70GHz&id=805
2.8ghz i7
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i7-2600S+%40+2.80GHz&id=869
Here's the benchmarks for the 3.4ghz i7 27 in. iMac (mid 2011):
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i7-2600+%40+3.40GHz&id=1
You will notice that is significantly out performs all the 21.5 inch imacs. However, the top of the line 27 inch (2011) is quite close in terms of performance. Price-wise, those are still selling for well over 2000 on ebay.
My friend has said that cpubenchmark is quite reliable in terms of gauging performance. While of course I don't know how true that is, if these are indeed accurate, it seems the 2012 mac mini's processor is extremely fast. Couple that with easier accessibility for upgrading, usb 3.0, and hdmi out, and my decision was made.
Don't get me wrong, It was really tough. The iMac just looks so sweet (even the 2011 models), but at the end of the day performance was most important for me so I went with the mini.
Made the purchase for my mini, ram, ssd, and audio interface two nights ago. I'm gonna wait for blackfriday/cyber monday to look for a nice monitor to pair along with it.