Greg:
That was an awesome score.... both the SF and the whole match (890).
I think it all boils down on these factors:
Reliability
Accuracy/Distance
Price
Reliability is paramount. If the gun does not go bang every single time you pull the trigger then you have to switch to a different brand. You also need to be concerned with battering your gun with high velocity ammo. Most target guns are not designed to use HV... so check your manufacturer for advice on that.
Accuracy/Distance. If you are shooting 50 feet, just about any ammo will be accurate enough. If you are shooting 50 yards, then you need to get a bunch of ammo within your price/comfort zone and ransom rest test it (if you can) for accuracy.
You might find that an ammo that shoots .75 inches and costs $45 per 500 and another ammo shoots .95 inches and costs $30 per 500... you have to ask yourself if the extra .2 inches is worth $10 per 500.