Best Version of Minecraft Server?

I think that 1.7 and the 1.8 are the best of the PvP mechanics, but if you are not interested in playing PvP you also can have fun playing 1.9+

1.8 or 1.12, never versions has very bad optimizations or very bad coded.

1.7.10 or 1.8.X because u dont have lag and u can make pvp good.

If you ask for my opinion, I would recommend either 1.8.8 (Use the paper jar or a fork of paper) or 1.12.2 (Same thing, use the paper.jar or a paper fork). These versions have the best server performance and most (if not all) major servers use it. If you aren't running a server with low ram (we're talking 8+ gb ram) and you arent expecting too many players, then sure, go ahead and use post 1.12 versions. There are tradeoffs for both of them. It really depends on what you want.

Honestly I think you should always stick to the last version, it's very nice to have an updated server, I know it might be hard to keep the plugins up to date if you're using outdated ones, but updating your server to the lastest give your server some prestige because most servers don't.
Now if you're afraid of perfomances, you might choose 1.12.2 since 1.13+ (mostly 1.14) are known to have a huge impact on perfomances.

.7.10 and 1.8.x support. I recommend this because it is the most stable version, most plugins support it, has support for older devices, runs better, and overall reaches a whole new field of players.

i use 1.8.8 whenever possible because
- its old and supported
- pvp is great
- it doenst use much resources

I have developed a lot of minecraft servers and the 1.8.9 is the stabilest version for an minecraft server

Optifine any day. It doesn't change the game much and boosts the fps. Its really good for low-end pcs trying to play more intensive maps.
I used to love 1.2.5 lmao simply because of the old tekkit classic pack.. don't know why but something about that mod pack is so nostalgic to me.

1.7.10 and 1.8.x support. I recommend this because it is the most stable version, most plugins support it, has support for older devices, runs better, and overall reaches a whole new field of players.