Ooooh, these posts are fun! The arena is built, the lines are up and KR is throwing the two heavy weights in the ring to fight it out!
I don't fly Cabs so can't comment on changes in quality in recent years. From friends who fly both brands - they both seem to be at the top in terms of quality. In my experience (flying SS, examining Cab) , the SS bars are simpler and more solid. I hear of a lot of folks buying SS bars to use on other kite brands, but I've never heard of anyone buying a Cab bar for a non-cab kite. I'm sure it's happened, I just don't hear about it.
This season I'm enjoying the Rallys. I find you have to pry the RPMs out of owners hands. They don't seem to want to leave them for another kite...or let you use theirs.
Only criticism I've heard from people who have left the RPM is it has a narrower wind range. I don't know if that's true, just what I've heard. There are Rally threads on here discussing it's performance- have a look at those and the 2011 SS Thread.
The SS kite quality has been consistent for years and the customer support is top notch. You have an issue...call your rep or the SS rider service line and they hook you up fast.
A have a couple friends who ride Switchblades and I get the same reaction from those who ride RPMs. The SB seems to be a kite that makes loyal owners who come back each year for the next revision.
I'm sorry if this reply didn't give you a definitive answer. This is all I have from personal experience. Demo.
Also, you didn't say if you are getting a new kite or looking to changeover your quiver? If you just want to add a kite, I'd stick with the same brand/model. It is easier to jump from kite to kite as conditions change if they behave similarly. Also easier to interchange bars and other parts as needed.