It all depends how you plan to use your satnav. If it's to simply navigate between a small number of stops letting the satnav choose the route then phone apps including Google Maps, Waze etc are fine. It's worth downloading offline maps, particularly if you are abroad, to reduce data/roaming charges.
However, when touring we regularly want to pick specific roads/routes, such as a particular alpine pass or fun section of road, and can often want to have have multiple stopping points for example coffee, lunch, viewing points and attractions. The route can be defined by "Shaping" points which direct the route along specific rounds and "Via" points" which are the stop points. Having created the routes (I use MyRouteApp) the resulting gpx files can be shared via email, WhatsApp etc and everyone can load their own satnav unit with the same route.
Both TomTom and Garmin units are fine and for the M3W I'd always recommend a motorcycle unit as it should be waterproof and better able to cope with the vibration.
There are differences in how Garmin and TomTom display the route and in the level of detail available for each planned stop.
Using a Garmin allows you to see the named Shaping and Via points along the route. When you start driving the route the SatNav only shows the named stop points to avoid an over cluttered display, eg Start, Joe's Coffee, XYZ Cafe for lunch, Car museum, Hotel . If you decide to skip a stop it's easy to do on the routing screen and the unit will reroute in accordance with the remaining shaping points.
A TomTom also allows you to load route specific gpx files but doesn't identify the stopping points but simply gives you a list of unnamed points along the route, eg Start, #01, #02, #03, End. This is often fine but you will need to spot your stop locations as you drive by and it's difficult to skip a specific stop along the route.
For me the Garmin is the better option due to the en-route information available.
