Let us do the math and see when wounding really is effective:
Round 1: X+Y
Cumultive W = X+Y
Cumultive O = X+Y
Round 2: (X+Y)+Y
Cumultive W = 2X+3Y
Cumultive O = 2X+2Y
Round 3: ((X+Y)+Y)) +Y
Cumultive W = 3X+6Y
Cumutlive O = 3 +3Y
Round 4: (((X+Y)+Y)+Y)+Y
Cumultive W= 4X+10Y
Cumultive O= 4X+4Y
Round 5: ((((X+Y)+Y)+Y)+Y)+Y
Cumultive W = 5X+15Y
Cumultive O = 5X+5Y
Round 6: (((((X+Y)+Y)+Y)+Y)+Y)+Y
Cumultive W = 6X+21Y
Cumultive O = 6X+6Y
Round 7: ((((((X+Y)+Y)+Y)+Y)+Y)+Y)+Y
Cumultive W = 7X+28Y
Cumultive O = 7X+7Y
Round 8: (((((((X+Y)+Y)+Y)+Y)+Y)+Y)+Y)+Y
Cumultive W = 8X+36Y
Cumultive O = 8X+8Y
Round 9: ((((((((X+Y)+Y)+Y)+Y)+Y)+Y)+Y)+Y)+Y
Cumultive W = 9X+45Y
Cuymultive O = 9X+9Y
Round 10: ((((((((X+Y)+Y)+Y)+Y)+Y)+Y)+Y)+Y)+Y)+Y
Cumultive W = 10X+55Y
Cumultive O = 10X+10Y
Feel Free to put your own values in for X and Y. X (which represents normal average per round damage considering all factors except for weapon damage enhancements (like flaming, the burst effects, wounding etc.)) is exactly identical every round so can be ignored. Y represents the bonus damage x the number the number of hits x the percentage of each of those hits, i.e. it equals the average damage per round from the weapon enhancement alone. For 1 successful hit per round with a normal wounding weapon you can see that not until round 6 does the cumultive W (wounding) damage equal the cumultive (O) damage using a flaming weapon for the cumultive O damage. Of course, wounding is a +2 effect and flaming is only a +1. For more than 1 successful hit let's say 4, there is a similar phenomenon, not until around the sixth round do things even out. However, consider after round 6, goto round 10. The difference between a flaming weapon and a wounding weapon is fairly significant. With one hit, the difference is 20 damage. With four hits the difference is 80 points of damage.
However, making this sort of comparison while legitimate limits the innovativeness of the wounding capability as opposed to the one time damage capability of a flaming or burst weapon. Using a wounding weapon to its maximum effectiveness means controlling a battle. A wounding weapon to be used effectively needs to draw out a battle. This can be done in multiple ways - focus on hit and run tactics: assuming both opponents have equal movement, this will slow down combat effectively drawing out the effectiveness of the ability of wounding. Also consider the opponent, realizing that the wound will not stop bleeding, a new priority is to get healing as opposed to doing something else. Where as the flaming damage happens and is done with, a person struck by a wounding weapon now has to use up an action (or an ally has to use up an action) to stop the bleeding. This is no small point either. Either casting a spell or making a heal check is a standard action meaning that besides moving, the opponent has to give up a turn (or someone on his side).
Moreover, knowing that healing is necessary, tactics can be used to predict this and plan to prevent it or counterstrike it. Finally, damaging multiple opponents with this ability (consider RttToEE when the party enters the original temple with all of the hobgoblins {were they bugbears?}) has great utility considering the ways of stopping the bleeding. Assume the four hits each against a different opponent each round for 3 rounds lets say. That's 12 opponents who now have wounds that won't stop bleeding. Perhaps you are the type of fighter who has focused more on defense than offense and can't dish out more than 10 20 points of damage a round - that means combat will last longer - wounding suddenly becomes much more attractive.