I've been playing extreme str and extreme agi build for a while. I'm by no means Phase or Dave or osmeone, this is what I've found:
30/8 - max ath, wm, ps and if. Using great sword, morningstar, bardiche Great for siege, great for non-bodkin archers, great for cluster fucks. Not so great vs any ranged I have to chase, caught in the open, vs mutiple enimies that keep distance.
9/21 - Used to have a 9/24, both points are the same tho. Max ps, ath and wm. Great for battle where there's enough room to sneak round the enemy, lighting fast strikes. The wpf and movement speed mean I can hit like a truck if I get it right. On the 9/24 char, I found Byz_Teeth standing still. I ran at him, slashed his head twice and he died. When I was dead I asked him what he had build wise. +3 guard helmet, some IF and 21 str. I can run away from anyone i dont like, cav are super easy to dodge, back peddle faster than ppl can run, can dodge ranged 99% of the time. Not so great on smaller maps, die in 1 hit mostly too.
I personally find these builds equally fun to play. They are both situational, but the str can work in more situations just because there's ALWAYS a clump of melee players. But I'd say my agi char is more useful, I can run into a melee, hit the best enemy players and dart off again, I usually charge archer nests, and as they can't kite I can stop them firing for 30 seconds until I get overwhelmed.
So really, if you want to get kills, go str. But a correctly played agi build is a million times more useful to the team.