There is nothing wrong with the dome sided Abus but I prefer the flat sided. One of the great thing about the Abu's is that they work very well with not that high of tolerances. I feel that the flat sided dual knob gives finer adjustment without having to rework the internals of the reel. For fishing reels I would say both could be tuned to operate about equal. I have a few Ultramag II and Ultramag III reels that I would never get rid of and they only have one knob to adjust the spool, except for my Ultramag III with the Benfield conversion. I love the ultramags but to get them field ready takes some tweaking of the internal workings, not hard to do just a little trial and error.
John