I’ve used TomTom and Garmin
Both have their + points, but for me the Garmin is better. The routing seems to be a bit better than TomTom and if you get the right Garmin model, it’s free map updates for life. The one I’ve got has traffic updates as well, which seems to work fine, but I’ve not encountered any really bad traffic for it to have re-routed anything yet!
The model I have also has photos of major junctions, typically A roads and motorways, so as you approach you see a photo of what’s ahead of you showing you where to go.
I also find the Garmin UI a bit better to use
The TomToms I’ve had have also had an annoying habit of identifying sharp bends in a road as junctions and sometimes it would ask you to ‘stay right’ or ‘bear left’ at daft times. Also found that roundabouts are sometimes not clear on a TomTom. Having said that, it gets you to your destination!
Both are easy to upload POI’s, etc to