That's not actually accurate. While Intel's higher-end 10-series CPUs were typically a little faster than AMD's 3000-series in games, when comparing these mid-range models the 3600 usually tends to be a little faster. This is in part due to Intel locking the 10400's clock rates lower than they do for their higher-end parts, so they lose their advantage there. And on mid-range motherboards, they are also restricted to slower RAM speeds. That's not going to be helped by the single stick of RAM in that Dell system, which will hurt performance a little compared to running with two sticks installed, though that Apex system doesn't appear to describe their RAM configuration, so they could potentially be doing the same.
Even so, practically speaking, the 3600 will provide virtually identical gaming performance, and is typically shown to be a little faster in other applications. And the 3600 is actually a little more energy efficient due to being built on a more advanced process node, and both processors should run stable. Both are currently good CPUs that will provide similar performance, so any decision should come down to the rest of the system.
And looking at that, they both have a 1660 SUPER, so I would expect the gaming performance of both systems to be rather similar overall. The Dell lacks an SSD though, going with a hard drive instead, which isn't exactly ideal in 2020. The 1TB hard drive does offer more than double the storage of the 480GB SSD in the Apex system, but overall system responsiveness won't be as good with the OS installed on a traditional hard drive, and load times in games will typically be around half as fast.
It does looks like Dell lets you adjust some things with the configuration though. You can select "16GB, 2x8Gb, DDR4, 2666Mhz" to switch to two 8GB sticks of RAM without affecting the price. That can net you a little extra performance over the default configuration since it should allow them to run in dual-channel mode, so it might be worth doing that. The options for upgrading storage (or most other things) are not priced well though, so if you want a secondary SSD or hard drive, it would probably be better getting one from elsewhere and adding it to the system.