First of all - Hello Everybody

Please excuse me if this was posted in a wrong section (there is no general section for SatNav systems) or if there was a thread like this.

My question is rather simple, as I am new to the GPS thing I would like to find out what system is in your opinion the most efficient (best?)?
I know there is plenty of GPS units, all running various softwares and mods, but Ive just got the Navman M400 and would like to be able to get most of it.
Update maps, cameras, POI etc. when necessary. My came with UK & ROI + 23 EU countries maps but some of them I want are missing.

I know my runs the Win CE and there are hacks to put other systems on, hence my question.

Any info would be great.

Thanks a lot!