Are you maybe referring to the 560 III? I don't think there is a 568 III.
The question really comes down to you need/want of eTTL. I consider myself a "Strobist", and I shoot with off-camera flash very frequently. But I rarely use eTTL. If you frequently shoot moving subjects then you'll want it, but usually I have the flash on camera for that. If my flash is off camera then I usually the subject is going to be more or less in the same place, in which case I prefer manual.
I ask because it greatly impacts which setup I'd get. If I was to buy from scratch, and only wanted manual, I'd get the 560 III (built in RF receiver) and a RF 602 trigger. And I'd buy one eTTL equipped flash for on-camera use. The 602 is manual only, you'll still have to control power on the flash itself. The 622s allow in-camera control, but personally I'd hold out until Yongnuo releases their new controller for the 560, it looks promising: http://flashhavoc.com/yongnuo-yn560-tx-revealed/comment-page-1/#comment-18260
IF you absolutely want eTTL off-camera, then I'd recommend the Yongnuo 565 over the 568. THe 568 adds high speed sync, again, something that I don't use a lot, but others may. However, there is a very significant price hike with the 568, it's almost twice as much. And at that price I couldn't help to consider spending a little more for a Canon 430 II. But at $90, the 565 is a great deal.
If you want off-camera eTTL then get the Yongnyo 622 triggers. I have them, they're ok, but I don't use eTTL enough to pull them out all that often. I prefer the small size (and 1/4" bolt hole) of the RF 602s.
One final note: I'm sure someone will jump in and talk about how unreliable Yongnuo flashes are and tell you to get a Canon 600ex RT. Most of the anti-Yongnuo rhetoric seems to be based on hearsay, not actual experience. I have three YN flashes myself (and two Canon), and I have a full set of both the RF 602 and the 622s. I've found the gear every bit as reliable as my Canon flashes.
