Here's a short article on the difference:
Personally, I use:
ProThera liquid fish oil (~2900mg EPA+DHA per teaspoon!)
Green Pastures Blue Ice Gold Therapeutics liquid (5000iu A, 500iu D in 1/5 teaspoon, plus some Activator X butter oil)
2-4 Tbsp fresh ground organic flaxseeds in my shake (I don't have this everyday)
If you're interested in the oils above, just PM me.