The quantity and ease of seeing the wildlife is better in Samburu Reserve than in the neighbouring Namyunak Conservancy (because the wildlife is drawn to the river running through the reserve). But there's not a huge difference in habitats or species between the two.
Elephant Bedroom Camp, in Samburu, is a fabulous, small camp. You'll see a lot of elephants and the owners are some of the worlds foremost elephant experts.
In Namyunak Conservancy, Sarara Camp is one of the most exclusive – yet low-key – camps in Kenya. There's slightly less wildlife than in the reserve but it's very close to the reserve and safaris from Sarara often enter the reserve.
The bonus with Sarara is exclusivity. You and the other camp guests will have the entire place to yourself meaning no crowding around animals (though that's rarely a problem in Samburu).
Unlike in the reserve itself you can do walking safaris in the conservancy and there will be more interaction with local people. The final plus is that by staying on a conservancy you will be actively helping to fund private/community conservation initiatives, which isn't always the case when staying only in a reserve or national park.
Overall then, I would opt for Sarara Camp, but I suspect it does cost more, so it might come down to budget!
