Shortened Military Scythe is longest range, Swords (bastard, long, heavy bastard) are all around and fastest, morningstar is heavy damage.
Honestly, I was 1 shotting medium armor with the shortened military scythe at 12 strength, which has 30 more length than the morningstar. You don't need to restrict yourself to it, but it is a beast and a guaranteed kill for the most part.
Couple builds I can recommend:
24/15: survivability and damage, able to ride heavier horses.
8 IF, 8 PS, 3 athletics, 5 weaponmaster
OR
Sack 2 ironflesh to max your athletics, or ditch weaponmaster altogether to max athletics and get a few shield skill.
Personally, I do higher agility so you can weave in and out of support situations, and better maneuver against enemy cav. Riskier on survivability. Also, higher riding and weaponmaster screws with your ironflesh and athletics, so you gotta decide if you want to min/max or not. I did really well with the following build, but I had a +3 Warhorse and +3 shortened military scythe, so my damage was inflated and I was driving a landspeeder.
15/21: 3 IF, 5 PS, 7 athletics, 7 riding, 7 weaponmaster
Anything inbetween. 15/24 or 18/21
18/24: 3 IF, 6 PS, 8 riding
^I've tried it. Extremely aggressive build. Stupid min-maxxing nonsense, but on a +3 Courser, the speed and damage was insane. Extremely dangerous and fun when you're winning, but if you get tapped, you're out of the game. I'd say stick to balance or the 24/15. build. Good luck, man, don't overthink it too much.