Hi,
The RFS2 transmitter is MUCH smaller and you´ll probably find it much more comfortable and mechanical safer on the RZ´s hotshoe. RFS2 is very fast (would sync up to 1/1500 with leaf shutter, so you have enough headroom for the RZ´s speeds). In case you should plan to buy into the broncolor system be aware, as far as I know at the moment it´s only the new senso packs that work with build in RFS2. We use the "old" RFS and found it extremely reliable. Hope this helps.
Cheers, Ulf