New Lezyne GPS nav

Agree with Macrophotofly's first and second post.

Using a phone is far from ideal (either as primary or secondary GPS) as you will wear down the battery. A good Cycling specific GPS, if properly charged, will last you a good 10hrs or more.

That said, if you are only doing shorter rides (1hr 30mins max) then a phone is probably all you need.

When I did my riding on my own a GPS unit was invaluable. The breadcrumb trail is useful, but it's only as good as mapping software used to plot a route. I've been out on rides on which my 810 has taken me through muddy bridleways - which obviously a 510 wouldn't be able to help you circumnavigate to pick up your plotted route (although, faced with the options, I chose to ride the bridleway in most cases).

I live in Japan and whilst I may be able to speak the language now, reading it is (and speaking it was, when I first arrived) another thing. So like many of my non-Japanese cycling breathren, here, a navigating GPS is nearly essential - especially when you are heading up some 1000m+ remote rindo (closed road) toge (pass) and want to get back to Tokyo for tea. Hence based on my experience and those around me in the local club -

• Presuming you have basic map reading skills, don't bother with turn-by-turn. It was designed for people who wanted to get somewhere in a car, at 30mph+ and think a map is something the passenger sitting next to them understands.
• Breadcrumb is okay but nothing beats looking at an overhead map with a nice coloured line showing you the way to go. If you miss a turn it's easy to look on the map and figure out if you can get back on your route at a later point, without having to retrace every step. More importantly you can often find the reality of the road doesn't exactly match what was planned on a website - if your road disolves into a rock-strewn muddy path then it is easy to look at a map on the screen and work a way round.
• The Garmin 800, 810, 820 and 1000 all work well for following routes. The screen size on the 1000 is a real bonus if you are following a map, although I survived perfectly well on an 800 for 4 years. Real world issues with Garmins are mostly the occasional lost ride - what we refer to as a GarminFart (more prevalent on an 800 than the  810 which in turn is more than the 1000 - can't comment on the newer 820. Personally I have not lost a ride on my 1000 after a year so far and only lost 2 on my 800 after four); battery life (you can't charge an 800 on the go without a special cable or it loses the ride; 810 and 1000 usually last around 7-8 hours max on map reading but can be charged up); and the odd interface glitch.
• We plan or share routes before we go out on sites like RWGPS and uploading them to a Garmin is simplicty in itself. Likewise getting maps for the Garmin for new areas/countries is simple these days - you can download free and legit from the internet (openstreetmap)
• Leave your phone for emergency calls, messaging the loved one that you will be home a tad later than you mentioned, and the odd photo. Get the Garmin to do work of guiding you around and tracking your ride.
• Bear in mind device size is not a problem if you keep it relatively parallel to the ground - point the Garmin (or any phone/GPS device) upwards like some kind of heads-up display and its adding to the air resistance.