iMac vs Mac Mini - which is more powerful?

I've got a mid-2010 21.5" iMac with the following specs...

3.06GHZ Intel Core i3

4GB RAM

ATI Radeon HD 4670 256MB

and a late-2012 Mac Mini with the following specs...

2.3GHz Quad-Core Intel Core i7

8GB RAM

Intel HD Graphics 4000 1536MB

I'm looking to use one of them for a flight simulator (XPlane 9.0 or 10.0)...but not sure which one would offer the best performance. Can anyone give me some advice on which to choose?

Thanks!

Andy