Best car GPS for use around Benelux region?

I've had a Tomtom model something or another for several years and it works fine, including in the countries you mentioned. Before that I had a Garmin Nuvi something or another, but it had a big problem picking up a signal. That might not seem very helpful, but my point is that you can have a great map but without a signal it is useless, so cover that base too.

Alternatively, use apps in your smartphone- There are offline maps available
I find traffic update with Apps much reliable than Tom Tom traffic or Garmin route

I have used the same TomTom 910 model for eleven years and am very happy with it. It has taken me all over Western Europe and through much of Eastern Europe. Occasionally it will make a mistake, but very seldom. Usually if it does make a mistake it’s because it is choosing the shortest route which is sometimes a third rate road. Whatever you get I would also take the “Safety Alarm” (read radar trap) option. It has saved me hundreds of euros. On TomTom I think it is around 40 euros per year. Well worth it.