SP2720 would be a great choice and I'm not just saying that because I have one. However, as RAM-Man suggested; I now run a Nuvi 765 in a waterproof case that offers more in the way of functionality. I have kept the SP2720 as a back-up and for SWMBO to use in the car as it's pretty bomb proof and has been a solid performer despite the odd issue which I managed to sort myself.
The Nuvi 765, now discontinued, can be had as a Garmin NOH unit (factory refurb, as good as new with warranty and the latest mapping) for around £110. The advantage of the 765, unlike most other Nuvis, is that it has an audio out jack into which you can plug a headset or, better still, the likes of an Autocom. It does have Bluetooth audio out of required, I've easily paired and used it with my earlier Autocom Bluetooth 1273 dongle but a mate of mine had issues connecting his 765 to the current
BTM-02A. Anyway, I prefer to have mine hard-wired as there are issues with using the 1273 for a purpose such as this that I won't go into here.
Whichever way you go; With both GPS and sat nav being bike powered you will probably need an isolated lead to connect the two, this will eliminate ground loop interference that you will otherwise probably get, this lead isn't cheap at £25-£45 from Autocom depending on which GPS you're connecting. For the 2720 you should be able to get one off eBay if your patient for £15-£20. Try with a plain lead first if you can but budget to have to spend the extra on the special isolated one.
Quest is a good unit but has small screen and relatively delicate flip out antenna, again you'll forever be stuck on 2009 mapping. As Kritou says, portability is a distinct advantage over the SP2610/2720 which are quite big lumps. Battery does last a decent time when fresh but in a used one it might be getting a little tired by now. (Nuvis last an hour or two on battery power so really need to be bike powered). Steer clear of the Quest II, despite using current NT mapping it has issues that in some cases make it pretty useless IMHO.
Buying a Quest 2nd hand; check that it's a European model as these have 243MB of internal memory where the US model has only 115MB. With no card slot that's all the mapping space you'll have. Euro model will fit all of the UK on, you have to chop and change mapping from your PC when going on tour and coverage will be limited on a long tour unless you take a netbook to swap mapping on the road.
SP2720s from the States present another problem, best to avoid unless you have a stomach for some command line stuff to convert it to a Euro spec version. I did this to my US spec 2720.
When buying a used Garmin you need assurance from the seller that he/she will de-register the unit with Garmin. Without that you won't be able to register yourself and update or unlock the mapping. Additionally you'll want all disks and unlock codes. Also be aware that in this era of downloadable updates you won't qualify to install the mapping that the seller has on the unit onto your PC unless he either hasn't bothered updating at all or has bought the updates on DVD. One time mapping updates from Garmin are around £50, however, you can get a lifetime mapping update card (official Garmin one) from the likes of Hantec or Pentagon for that money.
Nuvis won't come with Mapsource, you'll need to do a
slight hack install to get that onto your PC.
Good luck, it's a mine-field
Sort of naughty, but as Garmin have abandoned the users with non NT models some would say fair....
, Kritou can jump in on this bit if he wishes.
