What Is The Biggest Difference Between Fortinet FortiGate and WatchGuard XTM?

The main difference between Watchguard and Fortinet is the operating system, and how it uses the hardware features. The user interface in Fortinet is cleaner and we can adjust network and security needs in a logical way. Point-of-care only for SSO, certificate usage does not work sometimes, but this issue is handled in new OS releases.

Technically, watchguard can't scale in terms of performance and features protection for network, endpoint and cloud like FortiGate.

FortiGate has chipset that can support software turn on in the form of fabric technology.

Lastly, FortiGate has API which allow integration with 3rd parties technology to share policy, context and intelligence.

Fortinet FortiGate is a firewall with assured performance since it has ASSIC based purpose build processors. Also it has very reputed signature base worldwide. WatchGuard is good for SMBs where performance is not a major factor at perimeter security.

I have worked with only 2 FortiGate routers, remember them as having Sonicwall similar traits for management. Ok, but not that intuitive, so you had to learn and remember the management rules.
The WG units are more familiar to me, as I have setup dozens of these units in various models. I know the management Watchguard System Manager software more completely, so I understand it better, and remember it more.
The management is still just as exact as the Fortigate, but more intuitive in my understanding.
WG can be managed using a browser interface, but the WSM software is still more complete, in my opinion.

Fortinet fortiGate have large products portfolio as compare to watchGuard.

The difference is the poor performance that Fortigate has when it has all its services in use. Compare which customers have fortinet and which watchguards and see why the institutions in greatest need of security have watchguards.

UTMs option in fortiGate in better. High-performance network security solutions, users, and data from continually evolving threats.

Fortinet FortiGate is a firewall with assured performance since it has
ASSIC based purpose build processors. Also, it has a very reputed signature
base worldwide. WatchGuard is good for SMBs where performance is not a
major factor at perimeter security. So I suggest better choose Fortinet for
your requirement.

Fortinet are portable – cheap and easy to use

FortiGate is the best option for UTMs. Fortinet has most of the market share. Depends on the type of project that will structure, and the type of professional you have to support and maintain.

I would recommend FortiGate, efficient and not complicated at all. Also cheaper and support comes with it