Which BattleTech RPG edition should I start with?

[Nakura Chambers]

I'm going to try my hand at pen-and-paper roleplaying, and BattleTech has always fascinated me. I've been told to avoid A Time of War (the fourth edition) at all costs, leaving only the first three editions to choose from. I've been doing a fair amount of reading online and it seems like BattleTech fans are divided on which edition is the best. I'm really considering getting the third edition, because it has a lot of additional source material to use, but I'd very much like to hear what the community thinks, before making my decision.

I should note that I only plan on playing with a small group of friends who are also new to roleplaying, so using a modern ruleset (Third Edition or A Time of War) isn't really a problem for us, as we don't plan on going to official tournaments or playing with other groups (at least not for a while).