I've dealt with many firewalls, such as SonicWalls, UniFi, pfSense, and Cisco. We found SonicWall very confusing for the average network engineer or network administrator. I don't recommend SonicWall due to its hard-to-find auditing process for exploits. Although they have fewer exploits, when they do occur, they're significant.
With Fortinet FortiGate, you can access the whole firewall, with no hidden spots. pfSense is great, however, it requires a lot of manual work and has no Cloud Connect or easy management from an MSP's perspective.
Palo Alto is another option that's great, but their price point isn't for everyone, especially for medium and small businesses; a $10,000 investment doesn't necessarily fit into most budgets.
UniFi is another product we've started to use more alongside Fortinet FortiGate, as they have almost all features without a license, with advanced rules that are relatively inexpensive compared to Fortinet FortiGate's $1,500 a year.
Fortinet FortiGate and UniFi are the two firewalls we primarily deal with. My opinion is that UniFi has better integration and oversight of the environments compared to Fortinet FortiGate.