Tanzania + Zanzibar with 2 girl friends: Flashpack or book private tour with travel agency?

Two of my friends and I want to do this trip together but they have opposite travel desires.

One wants to get away from it all on isolated Serengeti game drives. Her dream is to stay at one of those isolated lodges out there with the attached pool.

The other is single (and looking for friends, since she moved far away from us) and she doesn't want to isolate ourselves so that she can potentially meet guys or new travel friends.

We are trying to decide between Flashpack's Wild Tanzania or booking our trip through Access2Tanzania directly. We have healthy budgets, up to 7k per person. Has anyone done either option, or what do you think about the relative isolation/mingling-ness of this itinerary?