Guides?

I'm not sure just how to advise you here, there's not a lot of similarity in the playstyle of a controller, defender and tank. I think you need to ask yourself what kind of character you like playing and then choose the AT that best fills that purpose.

Based on your forum registration date I assume you just joined us here on City? In that case welcome to the game and enjoy your time here, most of us are friendly and willing to help new players who want to learn.

I generally suggest a new player roll a Scrapper as a first, "learning", character as they're the most straightforward to play... you basically run up and smack the bad guys upside the head. Scrappers combine good damage with adequate defenses to be very forgiving of new player mistakes.

Getting more into specifics of the three AT's you listed, Defenders are mainly a buff/debuff character with moderate damage ranged attacks. The different primaries obviously play much differently but one thing to remember is that in this game our buffs and debuffs are very powerful and far more useful than simple healing. Yes, the Empathy set has some heals but it also has very powerful ally buffs. A defender is NOT a healer; even if he has heals his other powers are more important. As a FYI the defenders who are most sought after by experienced players are not empathy, they're Kinetic, Radiation and Dark. Of course all of the primaries can be useful.

Controllers primarily focus on, well, controlling the mobs by immobilizing them, holding them so they can't attack or otherwise preventing them from hurting the team. Their secondaries are slightly reduced strength Defender primaries so most anything a Defender can do a Controller can also. Most Controllers mature fairly late in their career becoming quite powerful in the 30's and beyond. Many of them struggle early in their careers.

A Tanker's primary purpose is managing the aggro of the bad guys, he wants all of the enemies shooting at him instead of the "squishy" members of the team. To this purpose the Tank has the best defenses and most hit points of any AT in the game and has several powers that attract the baddie's attention and keep them focused on him. His secondary contains melee attacks with moderate damage. Tanks are somewhat similar to Scrappers and they share many sets... the tank has better defense and less offense while the Scrapper is the opposite. Most teams will expect a tank to pay attention to everything going on and protect the members of the team so a tanker has more responsibility than a scrapper.

I'd suggest looking in the various AT boards for more specific advice about powersets once you decide what kind of character you want to play.

Once again welcome to the game!