Hi Robur
You say you don't want the distraction of music, with the Garmin it's main "extra" is an mp3 player, if you don't want it (like I didn't) the TT Rider V2 is cheaper
I can only give an opinion on the Rider so for what its worth.
The Rider only has Bluetooth, there is no headset socket so if using with an intercom system then that system needs a bluetooth adapter that will act as a headset.
There is a car adapter (around £30) that as well as being a mount point incorporates a speaker so you can hear the instructions, and a ciggy lighter socket power lead.
The unit comes in a big box containing the rider itself, a mounting cradle with Ram-Mount ball and a universal bike Ram-Mountkit. Also includes a power lead for permanent wiring onto the bike and a dc power supply for normal charging.
The box also contains a Scalar Bluetooth headset and DC charger unit (nothing included for bike charging though)
The headset attaches very easily to any helmet where you can move the padding away from the shell enough to slide a thinish mounting bracket up. This bracket contains a swan neck boom mic and a thin speaker on a flylead that attaches with velco inside the helmet. The bluetooth unit itself slides on & off this bracket so it can be easily removed for charging
In use I have found the rider easy to operate so far and the voice instructions are clear and precise, with the volume automaticaly increasing as your speed increases. The touch screen is responsive and again easy to use, even when wearing gloves.
There is no need to prepare a route, so long as you have set your home location just turn it on, select new route, destination as "home" as viola, it calculates the route from where you are (this is what all sat-nav should do btw) you can tell the rider to avoid motorways, toll roads, use fastest, use walking and use bicycle, though interestingly, for a motoerbike specific Sat-Nav there is no motorbike specific route !! (you know, scenic routes only and no right turns

)
If you have a pillion you can always purchase a scaler team-set which would link to the Rider and give pillion comms at the same time
Another feature of the rider, although you say you don't require this, is it will also bluetooth link with a phone and act as a visual intermediary between phone and headset, allowing to answer a call only if you wish
Hopefully someone will post a review of their Zumo so you can compare against real usage.
Any further info you want just ask