From what I've experienced around here, there's no definate reason to go shaft. They might be easier to work on, due to better diff access, but acceleration wise, they aint better than a belt car. Even not on a very tight technically track and with stock motors. And with a shaft car, you'll have to deal with un-even setup from side to side, to avoid torque steer.
There's around 5 Yoke SD's in our club. All of them break A-arms every now and then.
But as somebody else said, parts avaiblity really matter.
The good thing about XRay putting out new versions all the time, is it's quite easy to make a good deal on the previous version.
Hope this help a little.
Schumacher Mi5 - Sanwa MT-4 / RX-462 / KO Propo PDS-2123 - Nosram 5600 X-treme Saddle Pack - LRP SPX Zero/X12 17,5 - Nosram Stealth Touch Evolution - MAAS SPS 9250