His armor does give you more souls per kill but I don't recommend killing him early on. After you buy enough souls worth of stuff(I just usually but both armor sets he has and bonfire and buy until he has stock) of items he will start selling boss armor. Not sure but I think if you do kill him his tombstone may appear and you might be able to revive him after some time for souls. To get souls faster just help people with boss fights or farm the Giant Lord with any gear that gives you more souls.