In reply to Avinash Aujayeb:
I used Strava on my phone for a couple of years, works fine for recording a route and battery would last about 8 hours.
Over the summer my wife got a Garmin Edge Touring. It's like a sat nav for a bike, great for plotting a route and then guiding you round it. the round trip routing function is good for riding in new areas, say how far you want to ride and it will offer you 3 route choices, set off on the one you want to ride. Generally like it, only frustrations are when it tries to send you cross country on a road bike, and it occasionally decides to change your route halfway through a ride. Overall it is loads better than pulling a map out every couple of junctions to figure out where you're going.
I've now got an Edge 520. It's great for training, live Strava segments are fun, battery life is good, overall very pleased with it. Links to your phone via Bluetooth and automatically uploads to Strava when you finish the ride. Its weakness is route planning. You can load routes into it and they'll show on a map, but it doesn't give you any directions e.g. turn now. you have to watch the map the whole time, not as user friendly as the Edge touring.
I believe if you want the navigation and the training features you need to go for the Edge 1000, but that's a big step up in price and physical size. If all you want is the navigation, and are happy with manually uploading to Strava at the end of a ride, I'd go for the Edge Touring.