Well the issue with capsule probiotics is that usually they are already dead or for a number of reasons just do not include very active cultures. You can buy enteric coated ones that are supposed to survive past your stomach acid, but they are more expensive - I have never used them.
So I guess your right, kefir probiotics would be prone to stomach acid as well, sorry I don't have an answer for that one. However, kefir is much stronger than capsules, and frankly I am trying it because a lot of people have said it helped them.