I prefer Palo Alto over Fortinet FortiGate. Fortinet FortiGate is not the best firewall, but it is acceptable. If you have a budget to buy a firewall and Palo Alto is too expensive, then Fortinet FortiGate can be usable. As an instructor in Palo Alto Networks who knows all the techniques, I naturally prefer Palo Alto.
For a small company or branch, I would choose Fortinet FortiGate because it is cheaper and the features are sufficient. However, for more critical environments, such as government institutions or banks, where privacy and security are paramount, I would opt for Palo Alto.
In a hamburger topology setup with the internet side and internal side, I prefer using Palo Alto Networks on the internet side and Fortinet FortiGate on the internal side. This creates a multi-vendor environment, avoiding dependency on a single vendor. The internet side requires more security, hence I would go for Palo Alto, whereas the internal side would benefit from Fortinet FortiGate's flexibility and ease of use.
I would rate Fortinet FortiGate an eight out of ten.