Depending on what your fishing for you may never ever even get into your backing line.

the main reasons for a large arbor reels are
1. to retrieve line faster onto the reel.
2. to keep he line spooled at a larger diameter thus minimizing memory curl in the fly line.

I don't think they are designed to hold much more line, and for myself I don't consider that a selling point. That may be important tor heavier rods but they are usually outfitted with larger reels to match which hold more line.

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Be the heron!
Mike