I definitely do not speak from experience; I too am a new player, but I had to make the same decision and this is my analysis, based on what I've read and my examination of the power sets.
Necro and Ninja are melee. I wanted melee minions, so those are the two I looked at. Necros are resistance based, Ninja are defense/hide based.
I'm playing Necromancer and I'm pretty happy so far, because I like to stand at the outskirts of a battle and assist my minions. I leave bodyguard mode on for the alpha, then start ordering attacks on one target at a time. Because I've already got my target of choice highlighted, it's just one button push to mark him for taking down. I don't see how this qualifies as micromanagement.
If you turn your squad to bodyguard mode, Jounin hide and Smoke Flash should help you keep the aggro on yourself so the damage is split between everybody, which means not only do you get a large effective resistance bonus, but everyone's regeneration rate is added together, so you heal faster, too.
But if you're going to do the tanking for your squad, bots is the way to go. I don't know why but several dozen posters agree. Full bodyguard mode and keeping the aggro on yourself means the damage is evenly spread among all your squad, and, since everyone is suggesting Dark, the group heal is very effective since your squad will usually be equally hurt, you shouldn't be "wasting" heal on untouched minions. Focus your pool powers on personal defense and holding aggro, and you can be out on the pointy end while your firing squad assists.
I didn't look at thugs or mercs because I simply did not want to play them.
This is simultaneously advice and question. Anyone can feel free to correct me or add to what I say; it'll be good for us both.