Using TT Pro -46 in my 3D spirit;with 20/22 fuel,pullouts from hover are incredible with APC 12.25x3.75
I also have used 46 FX before but can't seen much difference between two.
But there is a point,TT is ABN(nickel plated sleeve) and FX is ABC(Crome plated sleeve),so you should give a little more maintenance,like using a little more amount of lubricant (like Thunder Tiger told)in your fuel(minimum %17) to keep the engine healthy.
There is also one more point there,the TT was the lightest one between my choices.
MDS 48: 500 grs
MDS 58: 525 grs
Magnum 46: 490 grs
Magnum 52: 502 grs
TT Pro 46(Preferred): 461 grs

Rifat