I'd go with the mini personally. The rotaries burn oil and are known to have problems. That and they have almost no torque whatsoever.
I see more Mini's in HPDE's and autocrosses than RX8s by a long shot.
1995 M3 Coupe - HPDE/Track Prepped - For Sale
1997 M3 Coupe - BMWCCA I-Prepared Race Car
2011 335d - Das Uber Commuter (35.1MPG Avg)