How does a Nano contract compare to a smart contract? Also, with Oracles being built into Hathor architecture, that seems like a big advantage?

Nano contracts are special opcodes that you configure to do specific tasks. So, you don’t have to develop/program a nano contract; you just have to configure it. The idea is that 80% of the use cases will be covered by just a few opcodes. This brings a lot of security to them since it is less error prone.