Old Land Rovers are not for everyone,
I love them (I work on them, they are my hobby) but they sure have problems and are not easy to live with.
If you want a daily-ish driver, go with a newer Land Rover for sure, still will take you to most places you dare to go.
Now if you have a soft spot for noisy, smelly, uncomfortable amazing offroaders, then go with a Defender, you will love it no matter how many times you need to repair it.
I had 6 Land Rovers since 1994, I have gone offroad with them in Europe, Africa and America, and only a couple of times, I had to call the tow truck.
I get mad at them, I hate them some days, but mostly I like this old things, if you keep it properly mechanicals are sound, if you try to build a crazy offroader with big tires and stuff, you will break it even more often...
Now addressing your question, first let's assume they are all in very good shape and well maintained:
The Defender of that age, will be the simplest to maintain and work on, the most uncomfortable, forget about heater or A/C (even if it has it, is mostly useless)
The RRC is amazing, very comfortable, A/C, heater should work OK, it could even have leather and some luxuries, it's pretty much like the Defender but refined (and more complex)
The L322 is a great truck, the couple of times I drove them, I love them, nice, comfortable, powerful, but if you plan to go overlanding far away from "civilization" forget about this one,...
That's my opinion anyway, so take it for what is worth...