Prophesy of Pendor is the most fun I have had in singleplayer, ridiculous mod but there is loads of interesting stuff to do. My second favourite mod is Sword of Damocles and my third probably The Eagle and the Radiant Cross, but that one never made it to Warband as far as I know.
I thought Brytenwalda was pretty boring because of the very limited item/troop variety, due to sticking to one culture and area. Those are the things that make a good mod for me, interesting troops and nice items.
1257AD is the most developed and most historically accurate mod out there, also has the most and best unique models and textures of any mod. As former developer I might be biased, though, but I haven't played any Medieval setting mod that compares to it, for any game.
I thought 1257 also a had a very limited item selection and troops looked very similar for most factions. I wanted to make myself a nice Sicilian knight with some cool Sicilian items but there weren't any. I haven't played it that much though. I don't think dozens of factions works very well with the Warband war system anyway. It is so much more interesting with a smaller number of factions.
Floris. Floris, all the way. And if you don't like the new combat animations it uses, there are guides on its forums to replace them with the native.
You can tick whether you want to use Native or new ones inside the installer now, I didn't but replacing the actions.txt with the Native one also seemed to fix the animations. Floris is a weird mod though, just a bunch of changes slabbed together, it doesn't seem a well crafted experience like Prophesy of Pendor or Sword of Damocles.
