As the closest Apple comes to a "budget model" Mac, the Mac mini usually turns out to be substantially less powerful than the larger, more expensive iMac. However, Macworld discovered via recent benchmarks that a build-to-order current-generation Mac mini can meet or exceed many performance marks of a stock configuration iMac.
The tale of the tape:
2011 Mac mini
- 2.7 GHz Core i7
- 256 GB SSD
- 4 GB RAM
- 2.5 GHz Core i5
- Standard HDD
- 4 GB RAM
Unsurprisingly, the Mac mini trounced the iMac at disk-intensive I/O tasks thanks to its speedy SSD. I've seen for myself the huge performance gains that can come from putting an SSD into an otherwise lackluster machine, but it comes at a significant cost; Macworld paid an additional $600 for an Apple-sourced SSD on top of the Mac mini's original $799 price.
Processor-intensive tasks showed remarkable gains for the Mac mini, with several tasks completing at almost the same time as the iMac. However, the iMac's far better graphics hardware handily bested the Mac mini's performance.
By now you're probably wondering why anyone would bother tricking out a Mac mini at a cost $300 higher than the iMac when the Mac mini doesn't come with a display, keyboard, and so forth. Macworld addresses this by correctly pointing out that the iMac's glossy glass display isn't everyone's cup of tea. The BTO Mac mini they tested also turns in similar performance in a far smaller form factor, which could be an important consideration if your workspace is too cramped for an iMac or Mac Pro.