Both the discontinued Futaba BLS 255HV and the newer (programmable) BLS 272SV have a proven record on the Synergy E7SE. I have not heard or read on anyone being limited by those servos. On the other hand, you have a point. Those Futaba servos are pricey, have one plastic gear (maybe sacrificial?), have a plastic case with the silly tab between the screw holes, and the speed and torque fall short compared to the newer servos.
For instance, the BK BLS-8002HV is cheaper, has a sexy metal case, has all metal gears, is faster, and has more torque. And it is the same physical size (20x40x37mm) and weighs only 5g more.
So yes, if I were to purchase a brand new set, I would purchase the BK's. But if I were to find a good deal on a set of mint condition BLS 255HV or 272SV (around $300 for NIB or about $210 for used), I would consider those without reservation.