Is it ok to use both Microdata h-entry and schema.org in the same template? Or better to use one of them?
This is a matter of redundancy. Google's validation tool only detects and reads these h-entry classes:
entry-title author updated
But appears to validate a broader number of schema objects. Whether Google uses them or not is very hard to determine and often changes. If you'd like to make sure it's using at least one, use both. If you're comfortable using one version or the other, then do that.