>>3782639As someone who's been there, here's the lowdown.
>vending machinesThey're all incredibly varied and there's distinctive "vending machine" chains, so you'll probably find quite a few that have a good selection you like. Automats are still very much alive in Japan, especially in more rural areas where there's not as many restaurants or konbinis.
>konbinis>LawsonAwesome sticker system, has probably the most well-defined "look" and aesthetic, usually reminds me a lot of Progressive commercials with the blue and white. Cute place and the ones that most girls would readily admit to liking. Also, has a lot of random tie-ins and sponsorships in media compared to the others, you're more likely to find anime-related goods being sold at a Lawson compared to the others. God tier onigiri and katsu compared to the others.
>FamilyMartThe most varied choices of food and just generally massive selection that it feels less like a konbini and more like a grocery store . Great place to go for finding ingredients on the go or something specific other stores might not have. Their fresh selections are alright, but nothing to write home about. As someone who constantly forgets an item or two for a recipe, I can always count on FamilyMart to have it somewhere that the others may not have. Also the most "online" of the main konbinis, has a direct partnership with Amazon for on-the-go pickup.
>7/11The "safe" choice, you can never go wrong with 7/11. It's like the standard to compare the average konbini too since it's everywhere and very consistent. You can be in Okinawa or the northern tip of Hokkaido and all the items will be more or less very similar and taste exactly the same. In my opinion, outside of Seicomart, it has the best fresh food. Selection can be limited if you want variety, though, since 7/11 likes being the most compact store compared to the others.
>Daily YamazakiThe dollar store version of the above. Don't go there unless you don't have cash and wish to be disappointed, the most similar to a low-grade convenience store in the states. It's where criminals fresh out of prison usually go to for a job, very sketchy in a lot of places, which is saying a lot since it's Japan.
>Mini-StopTheir ice cream machine is the best, but that's all I tried. Seems pretty alright, but that ice cream though... Perfection.
>THE CHAD SeicomartHokkaido-only, the absolute top shelf convenience store. Sometimes, it might be the only thing around for miles since it's in the wilderness, but it's like all the best parts of the above. The Hot Chef selections are simply the best and general service quality and foods are so varied that the others are lucky they haven't taken over Honshu yet. Also the only konbini where every single one I went to had a currency exchanger. Sold dishes and deli items of various locales, the only konbini I ate a burger from that didn't taste like a knock-off pseudo-burger.