I like the shorter length for my trailer, lower horse power requirement, and a better quality cut from what my research showsQuestion: Why do you want a flail mower?
It seems that you already have a mower deck for a high quality cut on grass. If you want to cut rougher stuff, you would be better served by a rotary cutter - for example a Land Pride RCR 1242 or similar mower should work with your BX (you are just under the recommended HP, so go slow in thick stuff). A rotary cutter is also much less money for a tougher mow.
OK - the flail is more compact. However, I do not think you will have much of a difference in required HP or width of cut with your tractor; I could be mistaken.I like the shorter length for my trailer, lower horse power requirement, and a better quality cut from what my research shows
As someone who owns and uses both a rotary cutter (RCR1884) and a flail mower (Del Morino Centurion Super 158) the flail is way easier on the PTO in terms of shock, way smoother and quieter, and definitely requires less hp to operate efficiently.I have a BX 1880 i recently purchased. I would like a flail mower. Will I be underpowered with a 48" flail? Kinda wishing i had bought a little more power but i wanted the 48" mower deck