1) You must be completely sealed against dust (ie usually zip), and
2) you have to you can wear on your belt easily.
During my research, there was ultimately a decision between the Rezo 20 and the apex 20 from Lowepro both (with whom I have always had very good experiences with my DSLR bags.).
For Apex 20 said the integrated rain cover. By contrast, the enormous depth (nearly 7.5 cm with S95).
For the Rezo 20 the shallower spoke (about 5.5 cm with spare battery in the front pocket), the 2 zippers of the main compartment (the strap to the camera can be performed) and the enormous expansion possibility the front pocket if desired. The 2-fold secured belt strap is awesome. Only (therefore a star deduction) spoke against the rain susceptibility because of unprotected upwardly extending Reißverschlusseses.
I am very pleased with the Rezo 20 and the S95 (with wrist strap and spare battery) fits perfectly into it.
Another tip: Because of the rain sensitivity I have merged two very small freezer bags in the front pocket mesh pocket that I can about tulips as raincover or as protective camera when taking pictures if necessary. The depth of the pocket thereby increases at most 1 mm.