Scripts that signal players to join an event at a specific times or often use a map, or an instance map to help players farm items. Example: Clucker event, Disguise event, Gold room, MvP room, Chess script
Scripts that rewards players for hunting monsters and/or gathering items, shops, or simply want to show simple functions and algorithms of scripting. Example: Headgear exchanger, Quest scripts, Mall NPC, Weapon dealer, Decimal Point System, Sorting Algorithm
Usually it is recommended to check which features you want/need, and which nemo patches you may want to use, after that, just pick a client that matches your needs.
For example, anything newer than 2019-06 would have the new guild emblems which is not implemented, so you may want to go with a previous date to have guild emblems. But if you want rodex, you would need at least 2015-05 or something around that. Another thing to consider are which nemo patches you may want to apply, as some won't work for some client dates.
Unfortunately there's no list of features/client date, but for patches you may check nemo.herc.ws