Weapon master is hands down the better PrC. There are two big reasons for this:
1 you can concentrate your feats into making your chosen weapon more effective. Using weapon specialization, Improved critical and power critical, you can concentrate a lot of damage potential into the weapon. On top of this the PrC gives you the ability to decide "this is the BBEG, I want to kill him extra fast." Yes you can do this a limited number of times per day, but you only NEED it a limited number of times per day. And the limits are pretty generous.
2 You can concentrate a lot of money into your weapon of choice. Having 50,000 gp in 5 different exotic weapons gives you 5 mediocre weapons to weild. Having 50,000 gp in one weapon gives you a rightious can of whoop-ass to weild.
As a fighter you have one mission: Do as much damage as you can every round. There are three considerations for achieving this mission:
1) Positioning- can you get to a place where you can hurt the enemy? Increased movement, tumble, climb and jump are all good for this need, but ALL of these skills/ abilities take second place to magic for meeting this need. Ideally, you should combine character abilities and magic to get uber here. Using a ranged weapon also takes care of this need nicely.
2) Damage per attack - Here the weapon master shines, becasue you will do more damage per attack with specialization, better crit ranges and a better attack bonuses. All things you get with WM. Mercurial greatsword is your weapon of choice here (but note the eratta on this weapon).
3) Number of attacks - again, weapon master has the advantage: Whirlwind attack is a prerequisite for this PrC, as is Combat reflexes. If you go with Ftr 10 and WM 10 you will even have enough feats left over to pick up great cleave (you always want power attack and cleave anyway). If this is your area of focus, then Spked Chain or the Duom are your weapon of choice.
I myself am working on a FTR 10 WM 10 master of Mercurial Greatsword with all these feats. He is fun to play, and kicks butt and takes names. He loses out on a few attacks, w/o the reach weapon, but he closes and kills very quickly.
I think that WM has it all over EWM. When push comes to shove, you will be more efficiently deadly with WM any day of the week.