Ever get the feeling you've been here before? Deja vous?
Manual trim will not make you turn better in any instance, in any plane. EW, MW, LW obviously matters not, nor does manufacturer.
Manual trim will (in certain instances) improve your performance by allowing you to trim your plane in a more desirable manner than the Auto Combat Trim. That's because the Auto Combat Trim works at its best in the middle ranges of the flight envelope, with an airplane in a "clean" configuration (gear up, flaps up, no assymetrical ordinance).
If you're flying in the middle ranges of the envelope, in a clean configuration, you probably can't manually trim your aircraft any better than the auto trim already does for you.
If, however, you violate those parameters by flying very fast, very slow, with assymetrical ordinance, by dropping gear, flaps, etc, you can trim the plane better with manual trim. Examples of these instances could be during landing, low-speed turning (expecially with flaps), at the top of ropes, while damaged, and while flying inverted. In these cases manual trim is nice, because the Auto Combat Trim may actually trim you improperly. An example would be while reducing throttle for landing, where the auto trim keeps you trimmed for the torque effects of full throttle, even though you've backed off on the throttle. Another example would be at the top of a rope, where you're very near stall, and the auto trim has your elevator trimmed full up, which is actually not a great trim setting for that manuever. Yet another is when you drop flaps, which also causes the auto trim to dial in full up trim.