There are 2 differant train of thoughts with what happens with the differant flywheels. I'll explain the differances first
61x has a smaller dia stator/magnets. The magnets are exposed, it is physicly 1/2 pound lighter than a T flywheel. Is easily identified by the magnets & the D shaped hole in the front.
62t Larger in Dia Stator/ magnets. Magnets are embedded, it's heavier.
identified by enclosed magnets & round holes in the front.
Both flywheels can be lightened by .5-.6 tenths of a pound (safely)
A lot of people opt to have X flywheels reather than T's because of weight. & then cut them lighter. Others opt for the T because they sight the "windage" from the X magnets , counter affects the lighter quality of the flywheel. Both stators are adaptable to the electrics & need to be run with their counterpart flywheel ( no mixing & matching).
In FS boats, The X is my choice for the weight differance. I have not seen a differance in the windage theory. overall, use what you have. the slight weight differance doesn't make a big enough differance to over come the cost factor.
ski ya, Paul