Thank you - comprehensive answer much appreciated!
If your Garmin is less than half the price of this, I.E. your Garmin is less than £100 that suggests you have a Garmin 25 which does not even have mapping. The Wahoo has a built in world wide map thus you can use it on holiday as well as in the UK. You can get full turn-by-turn navigation like the Garmin 820/1000 or the more basic breadcrumb trail of the Garmin 520. However there is one feature the Wahoo can do that NO Garmin can do yet. Using your mobile phone and the power of Google maps to pick a point on the map and the Wahoo will create a route and navigate you to that point. So if you have a mechanical issue during a ride, or just simply fancy a coffee, you can find a bike shop or coffee shop using Google maps then instruct the Wahoo to take you there. Whilst you might able to drop a pin on the map of a £500 Garmin it is not the same as a Google search and then your GPS navigates you there. Regardless, that is certainly not possible on a Garmin that costs under £100
Well I didn't know it and millions of others won't either so I left a helpful note for the OP which does no harm and he has taken the advice! So why don't you mind your own sarcastic business (annoyed) .
Recently switched from a Garmin 800 to a wahoo elemnt (same model as this deal but with bigger screen). Amazing customisation options and uploads rides straight away,and with great battery. Lots of vids online demonstrating the features. Very happy I made the change.