I wear Proselyte Top and Bottom on pretty much every task. The prayer boosts help you get the most out of your prayer when using the combat prayers, which you should be. If you don't want to waste the money on piety or the +15% str prayer. Even the +10% str prayer will make a difference and cost you less than 5 prayer pots per task. The defense isn't that bad, I think it's like addy, but it allows for cheaper use of the combat prayers and in return, faster training.