The use TomTom has for me during my trip is more routing options.
Yes, the biggest drawback of Google Maps is that you can't tell it to avoid certain routes, or prefer a certain road. Eg. If I know a certain route will be a nightmare it is very hard to force it to avoid that route, you end up needing to navigate to one place and then create another journey when you get there.
$80 vs Google Maps/Navigation for free is a fairly tough ask when it works so well. I see that's Europe. $52 for me for Australia.
It's £30.99 for UK & Ireland which is a good deal, or £39.99 for Western Europe which would cover everywhere the typical UK driver might go.