You can't go much wrong with either of those routes, although the road between the Bourg d'Oisans and Briancon is a major thoroughfare and can be quite busy at times. There are also a number of long-ish tunnels in the first 10 kms from Bourg that can be a bit intimidating on a bike. If you're coming from Briancon though, you barely notice them.
The Vercors is a hidden gem, lots of very scenic climbs and very quiet roads with little traffic.
You can't go much wrong with either of those routes, although the road between the Bourg d'Oisans and Briancon is a major thoroughfare and can be quite busy at times. There are also a number of long-ish tunnels in the first 10 kms from Bourg that can be a bit intimidating on a bike. If you're coming from Briancon though, you barely notice them.
The Vercors is a hidden gem, lots of very scenic climbs and very quiet roads with little traffic.