I just did a bunch of searching around with the same question a few weeks ago.
I ended up going with the ThorV2 which I finally got around to installing a X79 chipset in last night and wondered if I should have went with the 500R instead. Overall I'm pretty pleased with the Thor but a few nitpicky things are bugging me about it. If you can find it on a sale (I paid $85+tax) then it's an absolute bargain for the amount of cooling it does.
Cons:
First off, the height measurement on the case must be w/o the feet attached. It's measured at 22.84" tall, in reality it's closer to 24". That's about .3" taller than my desk allowed without moving a drawer.
Another problem I've seen is the quality of the case leaves a bit to be desired. There's just a few rough spots here and there that I've never experienced with my Lian Li and most higher end Corsair cases I've played with. Also some of the planning in terms of removing the top plastic portion of the case leaves something to be desired. Overall The 500r just feels more polished.
If your planning on installing a Corsair H-100 then just go with the Carbide 500r. I had to rig my H-100 around and install it outside of the screw holes (screwed through the vent holes in the top of the case with a washer). The Carbide is designed for the H-100 rad so it's a no brainer.
The grommets also tend to come off pretty easily while your pulling wires through. Read any reviews and you'll see this echoed many times.
They also included a switch on top that opens/closes the plastic vanes. It seems kind of like novelty to me, but it is kind of cool. It would have been MUCH better if they had raised the vanes up about 10-15mm since this would have allowed an H-100 rad to be mounted from the top instead of from the bottom.
One more nitpick...would it be to hard for Rosewill to install the standoffs prior to packaging.
Pros:
This thing is truly a monster case on a budget. It's freakin huge. This can be a pro or a con depending on your needs. Also it's really quiet for how much air it pushes. If your air cooling you'll be pretty stoked. Tons of flow going on here.
The smallest fan it comes with is a 140mm that's in the rear. It fit my AX1200 power supply pretty easily and I still have room for another 120mm fan in front of that. (another intake placed at the bottom of the case. From playing around with a 500r I've found that with my current system it would have been really crowded. This thread @ corsairs support forums supports my theory on this. A PSU like the AX1200 takes up most of the bottom of the case.
http://forum.corsair.com/v3/showthread.php?t=99933
The cable management is pretty decent, I've been pleasantly surprised by this and it seems fairly well thought out. Then again so is the 500r
This is more personal choice, but the front access panel seems to make more sense than on the 500r. Just easy to access what you need.
Again I've just started to mess around with the Thor so those are my initial impressions. Overall I would say the ThorV2 is a freakin awesome case for it's price range.