bit late but i have two pures so hopefully this advice will help you.
Onces a gmauler with 15 pray and ones a claw with 52 pray.
What i did first on my gmauler is stayed at 1 prayer, after a while like you're saying it gets hard to pk people with prayer, so i upped the level to 15 to enjoy that slighty, currently i've not gone onto 31 prayer on my gmauler as i have too much fun on it at the moment, so my advice on the gmauler is get the levels in steps. You might find you'll have more fun on a 15/31 pray acc then a 44 prayer as it seriously raises the pures combat.
Onto the claw pure it has 52 prayer, it gets seriously out matched by pures that are 31 prayer but obviously comes with the smite advantage. If i could i would of stayed atleast 31 prayer.
Like the other guy said, do your own thing and experiment with different prayer levels, only you know for sure what you really want and what works for you.
Hope it helped.