redearslider.com

http://www.beautifuldragons.503xtreme.com/Nutrition.html
This is a feeding list for bearded dragons, but was recommended to me as feeding guidelines for turtles b/c it's so informative.
It lists both romaine and red-leaf lettuce as something to feed rarely.
Pretty much every turtle site I've seen has it on the list of what to feed and I'm just looking for some clarification.

I don't see why both can't be given as part of the diet. I wouldn't give either every day (or even rotate them so that they get one of the every other day), but certainly occasionally would be OK. I don't give romaine that often, but my turts get some red leaf at least weekly (I don't give whole leaves when I offer it). I do push dandelions more than any other leafy green veggie, though.