I've had all three builds. 21/15, 18/18 and 15/21. They're all fine. 21/15 is probably my least favorite. Extra power strike is nice, but i seem to do better with athletics 6 or even 7.
Next gen i'm going with 15/21 again, i think. Maybe use that Winged Mace on foot some more... i love that mace. Riding 7 / Athethics 7 is gonna be fun.
Level 30 (4 420 577 xp)
* Strength: 15
* Agility: 21
* Hit points: 50
* Converted: 2
* Ironflesh: 0
* Power Strike: 5
* Shield: 4
* Athletics: 7
* Riding: 7
* Weapon Master: 6
* One Handed: 156