Brave Axe Cherche

Yes, I have a 5 star +Atk/-HP. I opted for 5 star since she's such a reliable unit for me and I wanted to eventually get her to +10 someday (I also didn't want to waste a 5 star exclusive Brave Axe+ on a 4 star).
But, since we get so many of her, it is very cheap to merge her at 4 star and get a +10 faster that way. It does also reduce her promotion cost and she's common, so if you want to change your mind, you can just 5 star her when you want while still getting use from her now.

I personally like the 5 star route.

I always 5* my units because who knows what you'll draw in the future. 4*+10 Cherche may be easy but then you're stuck never promoting her.

I guess it's personal preference, but I don't like 4* merges unless it's a unit that is marginally useful whom I don't care to waste feathers on

I opted to 5* her but at the time i was a noob and im a sucker for that shiny gold color around a unit.

But if ur ftp in the long run its better to keep her at 4* and merge her. She doesnt really have any exceptionally good skills to fodder off anyways. And ull just need to be merged to 4 to get the same atk as 5*

+atk -spd is one of the best IVs for Cherche. It is cheap to make her 4* +10, and she is super effective that way. However, there's something about the silver 4 stars that bother me... Besides my troll 4xReinhardt team (which does have a 4* +10 Reinhardt in it), I always prefer building optimal 5* units. Eventually, you will be able to +10 them all.

4 star merge her. She's not like Nino who would be suffer from not having gronnblade+. Since most of her skills are inherited from elsewhere you should just 4* merge her (she'll be more powerful than 1 five star cherche)