This is one of those cases where the build number isn't the deciding factor. 7.0 update 2e was built and released after 7.0 Update 3c, so the build number is higher. This is because the build number is incremented separately from the major and minor version numbers.
Personally, I use build numbers only as a fourth identifier. Use the major version, minor, and patch numbers as your main indicators. So, major version is 7, minor version is 0, patch is 3c (or 2e). 3c trumps 2e so yeah, it would be a downgrade to go to the newer release 2e patch.
