We just upgraded to Fios One. Previously we had the upgraded white Verizon router. With the upgrade equipment, they sent us a new router that looks like our first one (black & skinny). Should we keep the white Verizon router, or can anyone tell me how to check to see which is better? Sorry in advance for my ignorance!
Fios One is a set-top box. Fios One needs either a G1100 or G3100 as the primary router to work. The white router you have is the G3100 and the black skinny one is the G1100. They would both work for the Fios one box. Regarding which one is better, it depends on your needs. I would argue G3100 is better given its up to date WiFi 6 and MoCA 2.5. If the G1100 is gifted to you at no charge, you can keep it and repurpose it as an extender. If it comes with a rental fee, I would recommend you to return it because you only need one router.
As Cang_Household stated, both are great routers. The G3100 is the latest model and will be supported for a much longer time.
The other part of this decision is cost. If both have the same rental fee or are free, go with the G3100. If the G3100 costs more than the G1100, you might want to stick with the G1100 if you don't need/want WiFi6.