I didn't finish it because of one obscenly hard mission that made me get bored of repeteating it time and time again.

Thankyouverymuch then!:p
As for characters, let's sum it up as for my projects. [generally, they progress sloooooowly, since I write actual books, and so, have little time. They're mostly story by now, and when I have the story planned out carefully, I'll go to FREDding]
1.Legion - a [very] short campaign about Shivans, their legacy and how GTVA is doomed! DOOOOMED! It revolves around a bunch of SOC pilots stuck inside a system that is going to hell when Shivan legacy comes knocking. Characters are present, but there isn't much room for development because of few missions that will be in it.
2.CCCP - one psychotic Soviet Commissar is the main featuring character. He and his killswitch, that he uses frequently and liberally. Taking "Alpha 1's wingmen blow up fifteen seconds into mission" to a completly new, literal, level.
3.FS:SHMUP - Fidel Castro.
No, I am
not joking. [and for that one, I'm making table mods and new models already]
EDIT: oh, the same SN [no revealing!] officer will appear in a few missions, mostly combatting uncooperative FS engine.
"CURSE THAT DRAW DISTANCE! CUUUUURSE IT!"
4.Red Tide - Alpha 1 and Command, since the entire campaign is a game between the two of those. The rest is the support cast.
Generally, I must say that I prefer characters, and so use them. It's far more realistic. [and much more fun]