i need one of these oh my god. i absolutely cannot find the guy to give the pursuer's soul to, and I don't think i'll meet the intelligence requirement anyway. and I have no idea where any other ultra greatswords are. whole point of my build and i'm not even going to get one.
Pursuer's GS has those higher stat requirements, and the rarer upgrade materials, as mentioned. It really comes down to which moveset you prefer. The regular GS is also larger, though I don't know if that legitimately effects the range of attacks. I would say stick to the GS, for starters. I'm trying to remain spoiler free, but I know that there are more ultras to be found later in the game.