Well, a balance hole is only used to fine tune the ball's reaction (and make the statics legal), maybe 2-5% of the ball's reaction.  That will depend on the location and depth of the hole.  A shallow hole near your PAP won't change the dynamics of the ball since it will hit little if any of the core.  A deep hole that goes into the core will have a bigger effect.  So, filling a balance hole will negate whatever effect you made to the ball most of the way.  The plug material is a little lighter than what the ball is made of, and much lighter than the dense core that may have been removed.

 

For the less than PBA caliber bowler, I seriously doubt you'd notice much of a performance difference between a virgin ball and one with a weight hole that was later filled in.  Was the weight hole needed to make the ball legal, or was it added for performance?  Even if you fill the hole that's there now, you might want/need to add another in a different location.

 

I did that with my Black Widow Bite.  The original drilling did not need a weight hole to make it legal.  I wanted to get more movement down lane, so I added one based on BrunsNick's weight hole video.  I didn't notice much difference in the ball, so I filled that hole (didn't throw it after plugging to see if it rolled any different than it did originally - plus it wouldn't have been a fair A/B comparison anyway) and added a P4 weigh hole.  Now the ball rolls the way I want.

The success of plugging the weight hole will depend on type of ball, type of plug material used, and how deep the hole was.

1 hour quick plug is significantly less dense than the ball shell material, so using that will not restore the ball completely. Regular plug material is close to, but not quite as dense as most shell or core materials, but denser than the filler material used on some balls. So, depending on how deep the hole is, and whether the ball has filler between the core and the shell will make a difference. It is possible for the plugged hole to be heavier than the original material removed.

 

Bear in mind, though that any actual differences as seen in on-lane performance will be slight.

 

I can use a personal example on one of my balls, a Storm Rapid Fire Pearl. There is no filler used between the cover and core on that ball. I got it used with pin over MF(6"pin to pap). Ball had a deep hole on axis apparently to calm the ball down. For me, that layout is borderline for needing a low hole to avoid flaring over the holes. After plug/redrill of finger and thumb in same location, ball flared over the holes. Plugged weight hole with normal cure plug material, flare moved enough to be intermittant over holes. Still needed low hole.I concluded that in most cases, the ball will be close after plugging, but not quite what it was without the hole.

Hope this helps