Having just spent 8 nights in Selous this past June, I'd recommend splitting your time between the two areas you mention, especially if you can add a couple of days---something like 4 and 4 would work nicely. That would give you time in two different ecosystems and allow for variety in game-viewing and activities. There might be some special prices for June and perhaps early July, which could help with the finances and let you spend the extra time. I made use of the specials offered by Adventures Camps of Tanzania. I especially recommend Selous Impala, though the lower priced Lake Manze Camp is excellent too. You could write directly to Flo, Adventure Camps marketing director, for prices for next summer: flo.adventurecamps@sky.com

My report is given at: http://www.fodors.com/community/africa-the-middle-east/some-thoughts-on-selous.cfm

Nikao is recently back from Selous and Ruaha and did an excellent report: http://www.fodors.com/community/africa-the-middle-east/11-days-selous-ruaha.cfm

Yes, if you have the time, split it between Selous and Ruaha. Depending on budget, both have an array of choices, from camping, mid-priced lodges/camps or true luxury.

Last August I did 3 nights at Lake Manze (Selous) and 4 at Mdonya River Camp (Ruaha). I seem to remember the cost was something like $3500 with flights to and from Dar and I was paying a single supplement.

The Adventure Camps do seem to be the best value camps in these parks. I thought they were great- the only downside for me was that I didn't feel Old Mdonya had the best location- we seemed to have to drive quite a way to get to the most game-rich area which was around Mwagusi Camp. If I went back to Ruaha, I would definitely pay a bit extra and go to a camp in this area.

I notice that Adventure Camps now seem to have a second camp in Ruaha - Kwihala, and this looks like it might have a better location than Mdonya. It looks to be priced slightly higher- it seems to be in the same price bracket as their more expensive camp in Selous (Selous Impala), but still not as expensive as Mwagusi, for example.

Oh, and you can fly direct from Selous to Zanzibar- the price isn't that much more than to Dar.

Hi Sarah, We spent several weeks in Selous and Ruaha. Read my trip report and see photo link. I am happy to answer any questions you might have. Selous Safari Camps offer lodging in both -- Jongomero and Selous Safari. They are excellent camps. You can't go wrong spending a bit of time in each. They offer nice discounts (we got free air) if you book more than one of their camps. We also loved Mwagusi as you'll see in my report.

TC

as sdb2 already mentioned I'm indeed just back from a trip to both Selous and Ruaha. Stayed in the Adventure camp lodges and can definitely recommend them.
I don't fully agree on the comment of the location of Mdonya old river and it not being close to game. When I was there, plenty of game was around; Impala, vervets and elephant are almost constantly in the camp, as well as the occasional Kudu and even hyena. Lot's of lions close by and the camp also has a young male leopard in the area that's not shy at all.
In the morning we would tend to drive a bit further, to also have good chance of seeing cheetah, but it was also perfectly fine to stay near the camp.

On the other hand, I've heard plenty of good things about Kwihala, especially about the guiding. So that's a very good option as well.

In the choice of your camp, please also consider what you would like to experience in a camp;
Adventure camps are more 'basic' compared to some others, but for me that is one of the reasons to go there. I like not having electricity around (only to charge batteries) and no swimming pool etc. Gives me more the 'real wild ' experience..

I would try to go for 3/3 so you have a relaxed pace in your trip and have adequate time to see and do everything you like

forgot to include some links;

Adventure camps:
http://www.adventurecampstz.com/

My photo's from the trip
http://www.flickr.com/photos/nikao/sets/72157627739973912/show/

Some short video's that show a bit more of the camps and the tent you are in
http://www.youtube.com/user/chrisvdberge

And the trip report (also linked by sdb2 already )
http://www.fodors.com/community/africa-the-middle-east/11-days-selous-ruaha.cfm