With belt choices its important to remember than the shape of the pulley has to be suitable for each belt type -
Thread drive - the pulley needs a hemispherical groove for the thread to self centre and remain stable. Must be large enough for knot to go through uninterrupted. In terms of knots, I use with silk thread the knot recommended by micro seiki, the knot aligns itself automatically facing outwards from the pulley surface. I have checked my knots with various speed checking devices such as shaknspin, KAB speedstrobe and others and cannot see or measure any perturbation caused by the knot. The caveat here is that I use quite thin surgical silk.
Flat rubber belt - should ideally have a slightly concave pulley so that the belt does not wander up and down the spindle. The best belts such as those made for the original well tempered and the basis TT's are precision ground.
Tape - I have friends that have trialled various tape drives using mylar etc - you need a flat surfaced pulley with tape drive, and of course the pulley surface must be perfectly parallel to the side of the platter ( and the platter side must be perpendicular ).
As an aside I installed adjustable feet (3) on my Verdier motor pod - this enabled me to dial in precisely the correct alignment of the pulley to the platter - this is important for both accurate speed and stability of the belt as it rotates.
The original Verdier belt is round rubber - its main fault is that it is just a cheap O ring that is poorly made. Mine use to move up and down the platter by about half an inch as it rotated - this because the cross section was not round and quite rough. For a round rubber belt again the pulley shape needs to be concave so the belt does not wander up and down from the pulley.
I would assume the SOTA motor system and pulley is designed for a flat rubber belt as per the SOTA TT. I would assume Gallibrier designs his pulley for tape if that is intended. Any changes from the designers intention in terms of belt material may require a different pulley. Bear this in mind.
Personally I would probably try the SOTA Eclipse system because of the 3 phase AC. It's been in the market some time with good feedback. The speed controller system itself is very good. The original designer phoenix engineering also designed the motor drive and controller for the American Sound AS2000 TT which also uses heavy platter and air bearing. If you have a ton of money you could contact American Sound to see if you could buy their motor drive. I believe its a heavy duty version of the Sota Eclipse.