Hello 76GMC1500
I just had this conversation with a customer and we talked about same concerns so thought it may be worth bring up. The + or - standard of each method may have tighter standards in some cases and that would make one better than the other. Just the method an engine is balance in terms of being internal or external does not change accuracy or affect bearing life. The fact an engine has been balanced only asks to what degree of accuracy or tolerance. If internal and external engines are balanced to same spec then they are equally balanced.
I think an internal balance is less likely to get out of spec due to outer inertia ring on balancer slipping on rubber ring or the flywheel being damaged and needing replacement. The down side of average internal balance is larger counterweights creating more windage in stock form. The cost of heavy metal or Mallory is high and requires machining to install if converting balance method. Removing weight to control balance is best but adding weight is often needed. The removal of weight is also best so reciprocating weight is reduced and part of a performance mod anyway.