I think it depends what you want to do, e.g. look up & follow maps, record stats, etc.
The solution that worked reasonably well for me has been:
-- A tablet (or phone) with offline MAPS.ME installed. I don't follow this "turn by turn" but instead use the wifi when I might be at a hotel and use the offline maps for an occasional consultation.
-- A Garmin Edge 520 in my cockpit to record mileage and a customizable set of indicators, e.g. I like to keep track of time of sunset or climbing as well as general time/distance.
So the "screen is too small" doesn't really affect me since I'm not looking at maps on my Garmin 520 and when I do look at maps, I've got a larger tablet screen. I also don't find a need to look up those maps all the time (sometimes only in the evenings after cycling or sometimes at a lunch stop or tricky navigation point).