I'll just jump in as the same. I make about ten times more on SS than Adobe, more on Adobe a year, than Alamy.
Lifetime RPD Adobe is .82, SS .69, Alamy around $50. Earnings SS are about 10X Adobe or Alamy. IS is probably between SS and FT, but less sales.
To be fair, mostly different images on all, maybe 10% overlap. I've got many more on SS than Adobe and stopped uploading to Alamy just because of the time involved. But the reason I upload more to SS, first, than anywhere else, is because the return is highest in real money. I get to other places as I have time. I buy equipment and Scotch or whatever, with dollars not statistics.