I played with it for 10/20 minutes, on clipper and cybershape AC. On clipper it felt very controlled and spinny, fast when you need it to be. Overall too soft for forehand, but backhand it is like a upgraded Mantra soft.While on AC it felt slow and terrible. Maybe because i'm used to carbonado 145 but it really lacked in every depardment.
I can't agree that the Mantra Sound is "upgraded" version of Manstra S. I currently play the Mantra S (picked it up after trying Sound for a while). If you read the packaging of the two the Mantra S boasts a tensioned with the 'OCS Sponge'. The Mantra Sound's packaging makes no such claim that the rubber is tensioned though it is an OCS sponge. Mantra sound is 42 degree while Mantra S is 43 degree.
Speed Spin & Control values for Mantra S are - 146/132/84, while for Mantra Sound they are - 141/90/131 which I'd say is pretty accurate.
The claims made on the packaging are slightly different: Mantra S boasts -
"
OCS" | "
TransTension Sponge" | "
Built In Speed Glue Effect" | "
Tension Rubber" | "
Polyball Optimized"
The Mantra Sound doesn't make claims of any 'speed-glue effect' or 'tension'. It simply says -
"
ABS Ball Optimised" | "
OCS Sponge" | "
Light Weight"
In every way I'd have to agree that those are the main differences. The older Mantra S seems to grab, hold the ball, and spin it a bit better, but their top speeds are quite close. You just have to adjust your strokes a bit.