Owning a pair of both Atomics and ON3Ps, I can say a few things:
Atomic is well known for their skis having ridiculous edge hold. I can vouch for that. It's a little crazy how well they can hold on. They in turn tend to be stiffer.
ON3P makes skis that are super fun and are build like a tank. I cannot make any markings in my base, and the edges are really nice.
Since you already have a grasp on the Punx, you know a little bit about them. Skis generally don't tend to change that much year-to-year. I'm a real big fan of the durability and overall performance of ON3P products, so I would say go for those. Try something new.
Is there any possibility of demoing pairs?
While you're still looking, here is a good review of the Punx(may help, may not):
Here is a slightly less prestigious review of the Riches(may still help):
Hope that helped. Both are good skis, just keep in mind what style of skiing you enjoy.