I think for A to B journeys phone are fine. The real benefit to the dedicated sat navs are preplanning routes for runs at the weekend or on euro trips etc. Also the benefit of the winding roads feature on the tomtom is good for adhoc planning of trips when out and about when you don’t have anything planned.
I think you just end up with a preplanning system that works for the one you have. This is one of the bits where dedicated units really fall short for me; I’d need to take a laptop with me on trips because their UI’s not very good for planning routes on the device (and often there’s only about twelve pixels in the screen…), and the only option off-device generally seems to be to use some sort of wIndows app: https://advrider.com/index.php?threads/garmin-montana-or-gpsmap-without-a-laptop-android-apps.1338239/#post-35866029 for example. I still don’t quite believe that there’s no way to pair a phone with a modern satnav, but I can’t find anything to suggest it’s actually possible?
I think that whichever you’re used to you find easier to use so I’m really after what the objective benefits are so I can make sure I try out one that actually has those 
Yeah true regards laptop. That’s what I did on my last euro trip but it was fine as it gave me something to do in the evening. Compared to my tool pack etc taking a laptop in my rucksack was no bother