I don't mind bottom fill. I simply didn't find the various kayfun clones worked for me and gave them all away.I still use my protanks and subtank minis.
never got the protank even once!
I guess I’m not too fussed if bottom or top and as he says up and downsides. The kfun mini v3 is nice but a lot of my experience with top has just been fiddly. With the v3 I often forget to close the juice fills. The kfun 4 (horrible) was ridiculous twisting back and forth and I’d just prefer to unscrew it. Easier