Hi,
Currently MMI maps (v7.1) are best but their devices are good for normal usage.
Garmin device quality is good. But Maps are not up to date.
Tomtom - ok type. Didnt get any good feedback here.Check it directly.
Another less know brand is Navonans.
Navon .It has the best combination . UI from IGO-Primo and maps from Navteq. Even Garmin maps are from Navteq only. Check with them for the latest 2012 maps and a demo.
Don't go for satguide.
In MMI no free map update.
Garmin has 2years/4 map update free .
Other's need to check with them.
Experience both the device in hand and decide.
Currently i will vote for MMI with 2 year Map upgrade subscription. If you want good UI experience select their latest Sygic GPS devices.
FYI iam using the combination of MMI,Garmin, Igo for the last 5 years. you can PM me if you want any help.