Thugs gets bruiser, a melee hench, who is fairly durable. Poison gets noxious gas, a lasting PBAoE effect on one hench. Those two have great synergy, which is what makes thug/pois come on top against merc/pois.
Thugs are very strong MM team. I got Bruiser yesterday and he's a mean machine, as his first task he was tanking Leo McKnight (typing) longbow elite boss (red) with Gang War, it took awhile but there were no losses at all except for the Posse.
I had mercenaries but only for low levels so i dont know much. Cons for the thugs might be the low levels and then maybe early 20s, i felt weak - had to recall them many times in missions but that might be because of my secondary set and Aid Other isn't as good heal as Poison has (lack of healing thereof). Anyway if you take thugs, stick with them they get amazing 
Hellowie!
I have been thinking over a concept I have for another mastermind (I have a Necro' - Trick Arrow one too) for a few days, and I feel that I have finally perfected it. My only problem is, the concept fits perfectly (and I mean perfectly) with both the Mercenaries and the Thugs Powersets. I already know that I am going to choose Poison as my Secondary.
I was wondering if someone could please outline the Pro's and Con's of both sets and just give me some general advice on what they both exel at?
Thankyou very much!
The Rot Hood.