It definatly depends on what you want to do here.
I'm in the same boat as you are, but the ONLY reason I went Prot was so I could be a more stable tank in Instance runs vs multiple elites. In instances where you're fighting elite monsters a level or 2 above you, Prot has a huge defensive bonus and keeps agro more securely (versus monsters lower than you both can do about the same job, although Ret still needs more healing.)
I think it's safe to say that for leveling (especially in 2.3) your best bet is to continue Ret. TBH unless you're fighting monsters 2-5 levels lower than you, AE Grinding still goes relatively slow. With Ret you can take down monsters 1-2 levels higher than you in 4-5 good blows (about 20 seconds.)
In PVP Ret owns Prot, also. Prot is insane survivability but for pinpointing quest mobs Ret will help you much more. Fact of the matter is the more DPS you push out the faster you will level. I'd guess that Ret vs 1 is same DPS as Prot vs 4 or so -- and if you want keep mana you'll have to use Seal of Wisdom, otherwise you'll be taking breaks after 2 groups of 4, where as Ret can litterally grind forever in this timeframe.
Seal of Command is godlike because with a slow enough weapon, Judging it will simply be an afterthought when grinding, meaning you wont be casting for upwards of 25-30 seconds, giving your mana a ridiculous regeneration times.
Ff you want to tank instances instead of quest roll Protection with Sword and Shield+Spike, Retribution Aura, Blessing of Kings or Protection, and Seal of Wisdom.
If you want to do quests roll Retribution with a slow 2 Hander+Fiery, Devotion Aura, Blessing of Wisdom, and Seal of Command.