What is the difference between the 3 Hexcells games and which on is the best in your opinion?
I know you did not ask me but I've played the three, so here's my two cents:
All the games have the same MineSweeper-like mechanic in an hexagonal grid with minor improvements as the series goes on.
You don't need to follow an order as each game introduces the elements as if you did not know them before.
Hexcells is not a bad game but is on the easy side and, as a result, too short, IMO. It can be skipped.
Hexcells Plus improves a lot from the first one with other elements and very well designed puzzles which can be hard to get on a single try without mistakes. Get it on a sale or bundle.
Hexcells Infinite has a set of designed puzzles which is comparable to Hexcells Plus but it also has a puzzle "generator" with millions of puzzles. It can be seen as the more mature of the three and if you are only getting one, get this
. I did not like the generated puzzles as much as the designed ones so I would rate it only slightly above the second game but that's my personal preference.
TLDR: Get Hexcells Infinite. If you really like it and want better puzzles than the infinite ones you can get Hexcells Plus.