>>2819355
tl;dr they're all mid and you should only go if you have a specific reason for going or if you want to be the Cool Real Traveler(tm) and act smug around the Normie Fake Traveler because you visited what remains(4 medium sized rocks) of an old castle in bumfucknowhere where Date Masamune used to masturbate every summer solstice behind the east gate at exactly 15:36 and cum at exactly 15:42.

Solid 2/5 across the board, 3 if there's something in the city that you really want to see.
Fukuoka was the only standout because of the food stalls which made it unique.
You won't feel a big difference as let's say going from Boston to San Diego.
I can't comment on Sapporo because I've never been there but I will be spending a month there this coming winter season.

My take as a jaded resident who has spent around a week in each of those cities is that they're all the same and equally mid. You would need very specific reasons for visiting any of those places, and a lot of those reasons overlap such as. temples/shrines/castles.
However, if by city you mean the downtown area excluding the surrounding or nearby places, then the differences further narrow down, if you were dropped in the middle of any of these cities during summer you would be none the wiser. They all look and feel the same.
Infrastructure is the same, though I imagine Sapporo will be slightly different due to snow, similar to north/north west Tohoku where houses/buildings usually have a roofed parking area and entrances usually have a "玄関フード" to deal with snow/the cold.
Food is the same. Raw fish and salty noodle soup but with [this town's main produce].

There are very subtle differences which you would not notice unless you've been in all of those places long enough, for example Obon in the far north of Tohoku is more traditional - every single house had a gigantic lantern lit up at their entrance. You barely see this in Kanto, you wouldn't think that this is specific to certain areas unless you knew.