The balance is VERY important. You will break something very expensive with the wrong one.
5.0's since 1983~ish all used 50oz imbalance.
No doubt the Romac is aguably the best there is. They run about 250.00, though.
Now, if you don't need an SFI balancer, or want an SFI balancer but can't spend that much, the Pionner and the Professional Products have decent reputations.
I'd get the Pioneer HD non-SFI if I was just replacing a stock balancer.
If I was going to get an SFI, I'd probably splurge and save up for the Romac.
It's FAR more important to replace is SOONER than LATER if you suspect it is starting to fail....