I would say that ALBUMARTIST is a bad example for a field to be removed.
I cannot substantiate any problems in respect to
as any decent player uses ALBUMARTIST to group tracks for an ALBUM together if there are several different names in ARTIST. Otherwise you get 1 album per artist - which is often undesirable.
Coming to your observation in respect to performance: in general, a file gets rewritten if the padding space is not big enough any more when adding data to tags or when the padding becomes much more than the default padding space.
The underlying engine is the same for going the way with actions or using the extended tags dialogue.
So it would be a good test to first use one method and record the elapsed time, then restore the data and then do it again with the other method and then compare the time.
And perhaps you even add the 3rd way: remove the field via the tag panel.
