What I like about the Riva is that its a true 3.7, I dont get quite as warm of a vape on an Ego.  I use tobacco flavors, so I notice it a bit.  Others might not notice.  I do love it, though I have to say that I have NOT tried a true ego (I dont think I have, they ARE labeled arent they?),  and the ones I had were 650's.  It was supposedly an ego-t, are there clones of that too?  If so, thats probably what I had.