I aren’t aware of a GPS magazine, but I will give you a few tips.
Briefly, for the bike you need a waterproof GPS such as:
Garmin 2610, touch screen, cheap memory cards & PC mapping, large display not great in the sun.
Garmin 276c, push button control, expensive memory cards, large & sharp daylight viewable display, PC mapping
Garmin Quest, push button control, limited built in memory (Quest II is much better), PC mapping, small and sharp daylight viewable display, all the cheap ones have just been sold
Tomtom Rider, touch screen, large display, bike specific device, mapping on Tomtom data card for UK, rest of Europe is extra £’s, Bluetooth audio connectivity, no PC mapping.
That’s the current popular options; I don’t think there is any one GPS that’s a clear winner (yet)
Lastly, people do put PDA GPS’s on there bikes, some times in the tankbag, sometimes in a waterproof Otter Box (or what ever) but neither in my opinion are as good as a dedicated waterproof GPS.
Hope that helps, cheaper than a magazine too
(sorry If I stole your picture

)
Martin