When I travel, I usually do not have data anyway, my phone is on airplane mode from I leave until I return home. So a system that works fully offline is what I want.Osmand is brilliant for walking. It autoroutes along footpaths and trails, which is really excellent.
I wouldn't use it for driving though. It has no live traffic, unless someone has devised something very clever to pull in live data.
It could literally cost you hours routing you straight into a tailback.
Niels