1. Cheap 5" Chinese SatNav from GoMallGo on eBay               
2. TomTom Go 730               
3. Garmin Nuvi 360 Deluxe

I love SatNavs.  I had a Garmin Etrex which I used in the Alps in
2003 followed by a Garmin Quest, then my Garmin Nuvi 360,
TomTom 730 and GoMallGo.  The pictures left show the same
map location to compare mapping.

My Garmin Quest was good, it was waterproof, had a 20 hour
battery life, showed altitude, allowed routes with up to 50
waypoints  and recorded track logs.  On the downside the
screen was very small resulting in a poor view of the map.  But
the main issue was it did not give an audible warning of speed
cameras and locating Satellites was slow.

I bought the Nuvi 360 in 2006 and used it on my Tigers and in
the car for 4 years.  It could play MP3's and interrupt them for
speed cameras and directions.  I used the excellent
pocketgpsworld speed camera downloads.  The Nuvi is good
but no track logs, no altitude and it was a constant struggle to
get voice warnings to work using 3rd party add-ons.  Unlike the
others you can load Garmin Mapsource software on your PC
which is great for route planning but the Garmin maps always
seem to be at least 2 years out of date in the UK,  I upgraded
the maps once and vowed never again.  This Nuvi 360 only
allowed a route with a destination plus one waypoint which
was a real limitation.  Eventually it died.

My TomTom Go730 used TeleAtlas maps which I prefer
(Garmin use NavTech maps), the maps are more like a road
atlas showing built-up areas, water features, railways, parks
etc.  The TomTom could also show bye-ways and off-road
tracks which is great for an adventure rider who owns a Tiger.  
The TomTom could play MP3's and interrupt them for speed
cameras and directions.  On the downside I found the
TomTom harder to use than the Garmin, some of the routes
offered were poor (no wonder truck drivers get stuck in tiny
lanes)  and every time the software was updated I seemed to
have fewer features e.g. Why did my headphone volume
disappear.   TomToms can get moody and need resetting
much more often than Garmin and Traffic Master does not
work 99% of the time.  Battery life after 12 months was not long
enough to stop at a petrol station.

I find it frustrating that TomTom and Garmin are removing all
the great features I like such as a Jack plug (for headphones),
they no longer offer MP3 players, on their latest GPS devices
there are now very few customisation options, no track logs, no
altitude etc.  This is crazy when you think that a £23 GPS
application for my Android mobile can offer all these features
and more.  I had been looking for a SatNav with a larger
screen and a headphone socket.  I went for the 5"  item on
eBay for £70 from GoMallGo, it was a gamble that paid off, in a
word "Brilliant".

The GoMallGo comes with Nav and Go's iGo8 software which
uses the same TeleAtlas maps as TomTom.  iGo8 is
Hungarian and many users are Czech or Russian which
means that some of the websites are a little Er... Challenging.  
I suspect the software is ripped off and I was able to download
all the maps I wanted.  I find the iGo8 software so full of
features customisable I will upgrade to the real thing.  The
larger display is superb.  The standard iGo8 offering has so
many configuration options you really do need to be a bit of a
geek to make the most of it.  When you join the iGo8
community sites there are loads of options you can download
"Skins" which transform the look and feel.  I use the TomSoft
updated version of the diMKA skin which is wonderful but it
took me 5 very frustrating evenings to get it working.  
TIP: Make
sure the skin is the same pixel size as the GPS unit, else it will
not work. The configuration options are awesome and just
look how good the mapping is in comparison to the Nuvi and
TomTom, 2D or 3D it is so much better.  On the downside I
can't loan this GPS to anyone because it takes a long time to
learn and I do not want to lose my settings.  If you are not a
SatNav or techno geek stick to a standard mainstream GPS.  If
you want lots of configurability this is the one.  I forgot to
mention that the routing is way better than TomTom.  Initially I
only used the GoMallGo in the car, however my TomTom got
stolen in October 2011 so I have bought a second GPS from
GoMallGo for the Tiger, this later version has a metal case , it
was cheaper , has later maps and I love it.
TIP: Get a MediaDevil Matte protective film from Amazon to
reduce reflections, I ordered one too large (iPad) and cut it to
size for my GPS, Netbook, phone etc

Apart from my early Etrex and Quest none of these SatNavs are
waterproof but there are ways round this for the ingenious
Adventure biker.  
Comparing the SatNavs that I have used
Adrianmolloy.com Home Page
Triumph Tail Pack, Tool Kit, Handguards, Fender Extender
Motrax Chain Oiler, Extended Chain Guard and Skidmarx Hugger
Heated Grips, Sheepskin, Cargo Net, Triumph Sticker on Tail Piece
Camera Bag, Bar End Weights, Sony Radio, Accessory Plug
Acumen Gear Indicator
Some of the other Bikes I have owned Part 1
Some of the other Bikes I have owned Part 2
Some notable Bikes I have ridden over the years
I made the GPS Sun Visors myself from 2mm plastic
sheet, bent over a wooden former with some help
from a blow torch.  All held on with thin strips of velcro.
My old Garmin Etrex
from 2003
My old Garmin Quest 2004/5