Beyond that there is how immediate the life gain is, how much you get or can potentially get, how cheap the card or effect is and how hard it is to disrupt
Oh, and it goes infinite with copy spells and magecraft
The overall strategy is to enjoy Cosimas ebb and flow, control the board, stay alive long enough to draw the combos and try to pop off, all while protecting your plan with counterspells
Then you can spend three and draw 7 cards, exiled by his effect, then spend another one and pay 7 life to draw them from exile
Authors note: The busy Magic release schedule made it impossible for me to dedicate an article to The Lord of the Rings: Tales of Middle-earth Holiday Release, but I did do a Commander Spotlight article for Galadriel, Light of Valinor
The color identity restriction means I'm excluding powerful transforming double-faced cards like Archangel Avacyn and Brutal Cathar since they have red backsides