The burning question when starting a layout: sectional or flex track? In N scale there are many brand options available, which gives modelers a number of options for their layouts. But unless you are a beginner building a small layout, you should choose laying track yourself over sectional track with a plastic roadbed.
There are many benefits of laying your own track, including the appearance and flexibility. The appearance of flex track is far more realistic than sectional track with a built-in roadbed, as the plastic is rigid and uniform, unlike real track. Also, when it comes to Kato track, the tie spacing is not correct for US railroads, and flex track will look much better, especially up close.
Flex track, as the name suggests, is much more flexible and allows for more realistic layouts than sectional track. The rigidity of sectional track keeps you from being able to lay track freely. When I was planning my layout with Kato Unitrack, I became frustrated with the rigidity of the sections, and I could not settle on a plan. Eventually, I found something that I could live with, and I kept the track because I could not sell the track for enough to build a new layout with flex. Using Kato Unitrack is not the worst thing, as you are up and running quickly with minimal wiring, but this means there are limits to what you can do with it, and it is also more expensive than flex track. So unless you are building your first, small layout, then flex track is the way to go.