Unfortunately SDM is a slow AF mechanism, but the 50-135 is optically excellent.
The Tamron 70-200 (which I use) is very good optically, has longer reach and don't hunt as much in AF function.
Focusing speed is maximised when there is a high contrast target being used to focus on, and as such I do believe AF technique is a most important aspect to ensure fast and accurate focusing, no matter the lens.
I shoot concerts often, and get sharp results, no matter the camera, as long as I use those techniques when shooting. Of course, there are times when the subject is moving too fast and the shutter release lags behind the AF lock for the moving subject, but generally, if I have settings right to freeze action adequately, I can get decent results with the Tamron 70-200, FA 77/1.8 and FA 100/2.8 macro in concert situations.