To an extent, the choice is a matter of taste. As the gauge gets smaller, the harder it gets to ensure proper register and a sector plate become better as at least one end is tied down.
The downside to both systems if one is using an end to end layout is that the trains will need to be reversed. Some folks build a cassette system into their traversers so the entire train can be picked up as one.
Shown below is a traverser built for my layout which was used until all the modules were complete and a rear fiddle yard installed. It worked quite will but our 9mm gauge asked a lot of it.
I think the sector plate is really useful functioning as the "missing end" of a runaround, or loop. It's also useful to provide routing to a fiddle located behind a backdrop. A traverser can have multiple tracks and so provide for some car holding and more complex "off-the-layout" operating schemes at the expense of some real estate and construction effort. As always, there are many terrific examples on Carl Arendt's wonderful 'site. The layout design may naturally favor one over the other. Have fun!
____________________ If it moves, tax it. If it still moves, regulate it. When it stops moving, subsidize it.