Ash

Thanks for the feedback all, I'm mostly looking at what I can logically achieve. I don't spend enough time using my stamina potions and grinding the specific events and such to get enough stuff to be able to merge enough 5*s. I don't pull enough for example, nor do I spend any money in the game. So pulling 4*s and merging is more logical for me to push for as they obviously have a higher chance to pull them (I already have a couple +7s for example)

My current thought process is pulling on units I really want and on banners where I can get dupe units for the 5*s I've luckily already had a duplicate of.

The others answered (also I love you nerds lol) so just wanna say personally since I play casually I tend to just wait till I can get the 4 stars to 5 star and merge. Which is why I only have 4 +10s atm despite playing since almost launch.

Not much more to add on the theory side, but want to comment that personally I would rather invest on merging 5* units, on the long run they would reach +10. It's a sort of long-term investment. Besides, once they reach +5 they become as good as a 4*+10.
Then again, I have not played it as much lately, and I'm too conservative to even merge my 5* exclusives, so take that as a grain of salt xD