Yeah, I owned a 231 RX8 for 4 years. Traded it in for the Zed 2 years ago.
First I'll start by saying the oil thing is not an issue. and everyone who has owned one for longer than 5 minutes will agree. I used about 1 litre every 1200 miles. Which when purchasing from Opie Oils, costs bugger all really.
They are quite a thirsty car, the RX8. I find that on motorway driving the Zed is much better on economy.
However, the Rex is a pain in the ass to drive smothly in heavy traffic. Very jerky car.
For spirited driving on twisty roads, I'll behonest and say the Rex was better than the Zed. It feels ligther and more adgile. Begging to be thrown into corners close to the redline in 3rd.
The interior is better in a Rex than in early Zeds, but from 06 Id say that the Zed is better, and way more comfortable to drive.
tbh, its one of those discussions that could go on forever.
My suggestion would be to test drive both, on more than a few occasions, and see which one you really want to have another go in.
Have a search on the forum for RX8 - you will see quite a few threads comparing them with the Zed. And many comments from former RX8 owners who have came this way. There arent many owners who went the other way....
Hope that helps
Al