Between Mesa's STR440's which are probably Electroharmonix and Winged C's, the winged c's have a much bigger well-defined bottom end, too much in some of my amps, actually. The top end is hugely detailed to the point of harshness in some situations, but probably depends on bias level to some degree.
I find the winged c's to be too much of a good thing in my amp, but didn't love the EH's either...I moved from 6L6's to EL34's to 6v6's and am happy in the 6v6 camp. That said, I really like Tungsol RI 12ax7's and 6v6's, so if Sovtek is putting the tungsol at the top of thier lines, I'd give a Tungsol 6L6 a buy and try.
The TAD WGC tubes are really old school like a GE and seem to be a good balance between clarity and warmth. If you have the JJ's then you might find the Winged C to be a lot the same, the Tung Sol are somewhere inbetween the JJ/Winged C and the TAD WGS's
Just my experience