I've had two Sigmalux (50mm/1.4) before and they were wonderful. I only sold them for the 50L upgrade. If you don't mind with MF thent the SMC Takumars are very good. The colour swirls are very nice addition. Of course Zeiss 50/1.4 ZE is just stunning with it's microcontrast.
If you need AF just go with Sigma or maybe just wait till Canon does the 50/1.4 II update which is... (not so sure when)