Using SoR/JoR as your main damage seal, you get 9/10% of your +dmg as seal DPS, and 7.3% of your +dmg as judgement DPS (when judging every cooldown).
This means you get somewhere around 1 DPS per 7 +dmg. On the other hand, 14 AP (7 Str) gives you 1 white DPS (mitigated by armor, but does not require mana).
Knowing this, you'd get the highest DPS (and presumably best grinding) out of items that give the highest combined offensive stats. (MP5 is also something to consider, since it means you can use abilities more often)
For example, look at Righteous Helm (
http://www.thottbot.com/i28285) and the Ruby Helm (
http://www.thottbot.com/i27505).
Righteous gives you 23 +dmg and 6 mp5. (ignoring sockets)
Ruby gives you 28 +dmg, 10 mp5, and 25 Str.
Clearly the Ruby Helm gives you higher damage stats, so it'd probably help your grinding more. The defense stats on Righteous could help you live longer, but you'd also take longer to kill things, and paladin downtime isn't a big deal in the first place. (BoW, make use of your spirit, heal yourself every once in a while, and you'll never have to stop)
And don't overlook mana regen.
http://www.thottbot.com/i28108 is probably the best grinding trinket in the game for mana users if you can kill things fast enough.