I have a Garmin 500 that came with my latest bike .... it has the cadence sensor and speed magnet (not sure why you need the magnet sensor as it uses satelites to work out your speed)
I've created a few courses, but don't really get on with the 500 and will be buying a 1000 at the end of the month
firstly, it uses 'breadcrumb' mapping .... it does not show side roads, and is merely a black line. If you take a wrong turn, you get a message / beep saying 'off course' .... when you turn back, you are still 'off course' until you find where you went wrong and carry on riding in the same direction.... you can only plan and use routes that you download from your computer beforehand (i.e. you cannot punch in a postcode etc like on a car satnav)
the screen is too small for me. But saying that, many people who I follow on Strava are still using these. I'm old and get lost easy. Suppose it's ok if you know the area reasonably well and just want to use it in case you take a wrong turn
I need something that works similar to a car TomTom .... punch in a postcode and it will take you there.... or if you take a wrong turn and continue, it will reroute you, or you go for a long ride without using the mapping and when you get halfway, click the 'take me home' button and it will work out the route.
some people really like the 520 ....
for £169.97 that you are looking to pay for a 500, you could possibly get a used 520 or even a better model than the 520 off
ebay?