I have the KK rock and roll, and I love it. It does take a lot more space, but luckily, I have a basement training room where I use it so size doesn't matter. It's easier to put the bike on and off with the latch compared to the road machine.
The biggest reason for the rock and roll for me was the torque that could be added on to a fixed trainer to a carbon frame. The rock and roll moves with the frame, thus allowing one to get out of the saddle and "rock" the bike if needed.
The front lift with wheels is key too if you want the rock and roll. It's a bit pricey, but instead of getting a cheap one and replacing it in a year or two, better to spend that extra money and get a good trainer. (same philosophy about a bike)