Hi! I'd like to drop some lines in the Tree because i used so much on my reasearches, now I believe i must return some data on Safaris!!!!
Firstly i did the northern circuit, on a 5 days safari, with Sunny's and it was really great. I was alone, and managed to find someone in the forum, and they managed to put us along with another single person in 2 weeks time. Our driver and also guide, Esthomi, was really nice, showing us loads of animals (we did manage to see the big 5, plus massive numbers of lions - 64, 3 leopards, 6 cheetahs, 3 Rhinos,3 cerval cats, 6 jackal... ) and our cook, Hamad, was superb, we even had pancakes and crepes! Esthomi managed to drive us a little bit out of the beaten treks, and so, we could have all this crazy numbers of animals. The highlight was a lion hunt that we saw, because our driver told us to be patient when we all were feeling tired of sun and hungry. We have to thank him so much!!!
The second recommendation refers to Selous. Most people forget about the southern circuit, but this was SUPERB. I stayed in the only wild camp that exists now out of the park - which turns to be quite cheap - US$ 10 per day to camp and also they charge US$ 30 per the mud hut they have and is very comfortable. It´s called SELOUS River Camp, and I found them here in the forum, so if you look for http://www.selousrivercamp.com/ you can find them. I know that when they are in the bush they cannot answer emails, so if you are interested pm me and i can give their mobile. Katie and Kenny were the BEST hosts and also they managed to drive me in their 1952 land rover, which was great too. We drove sometimes hours without finding any single car, so i feel the experience was more intimate. Even if it´s much harder to spot animals than in the northern circuit, you also see lots more of girafs and elephants, and the bush lions, which are amazing and so muscular, because of the time they must be hunting in such big area.
So, these were the two companies that i used, but basically if you want good tips on choosing a safari company, i read on my guides, Rough Guides and LP and also searched here on the forum. I was on a budget, but the level of service i had was EXCELLENT. I also met lots of people who got in Arusha and were meeting those flycatchers offering great deals. All of them very disappointed... So, i guess sometimes paying US$ 50 more is much better than trying to save money. After all, safari in Tanzania is VERY expensive... If you such in a big budget, ask to see cars and drivers before, because i even saw one french couple who decided to go in a day trip to Arusha National park with a small company called Jackpot Expeditions and their jackpot turned to be a cook driving their car....
Good Luck!!!!!!!!!!!!!!!!

brtata
Pro tip