The T3 versions of the styles will work best because all the voices in the T3 are in the s950. The T4 version of the same style may include a voice that's only featured in the T4 such as a drum, vocal, synth guitar or string voice, if that's the case the s950 would either try and substitute it for a similar voice or if it can't it will have no sound at all.

I would only use the T4 styles that are exclusive to the T4 (eg, not found elsewhere) and tweak them otherwise the T3 version of the style would sound best.