Sat nav or cheap Android phone?

Hi all, I've been using my work smartphone on a Quadlock mount for the last few years but I've had to give it back as I've left my job. I still need something for navigating on when on my bike (can't use my personal phone as it's a Samsung flip), so I was considering either a cheap mobile from CeX/eBay (to be used exclusively for this purpose) or a dedicated Sat Nav (TomTom/Garmin etc). Any advice?

Do Android phones need to be of a certain spec/age/OS in order to still be able to use Google Maps?