I have the 645''s on a Funtana and a Showtime. I used those based on recommendations from other guys that were using them.

Your probably not going to notice a whole lot of difference considering we''re talking about 5 hundreths of a second at 6 volts. I seem to remember reading somewhere that "quick" human reaction time is about a quarter of a second at best. I wouldn''t consider 645''s on the slow side either. The *high end* Hitec servos that claim high speed such as the HS-5955 are also only a few hundredths of a second faster that the 645''s. I know a couple of guys that use those on their jets and large scale stuff without any complaints. I guess it just comes down to what you need more, torque or a quicker rotation which you may not even notice. Even with the latency of the 9C running dual elevator servos on the showtime the plane reacts what I would say is instantly. I''ve never said to myself that I wish it would react faster.