There is a wide variety of blank media options on the market, but when it comes to dual layer options are far less and the cost is much higher.
A dual layer disc consists of two layers within the dvd which allows the disc to hold nearly twice as much data as an ordinary writeable dvd. The disc takes twice as long to burn depending on speed as it writes each layer separately.
I've bought cheaper brands in the past which result in a cost effective price to begin with, but when a number fail it works out more expensive.
I have now been using the Datawrite Dual Layer DVD+R for 12 months and it's extremely rare I end up throwing one away (coasting). However ensuring the disk burn perfectly nearly every time requires a couple of checks....
1. Always ensure your firmware for the drive is the most up-to-date
2. Don't exceed the recommended manufacturer burn speed for the disk.
In this case the burn speed is limited to 2.4x, burning any faster may create a successful burn, but the life of that disc will be shorter than when burnt at the manufacturer's recommended speed.
These aren't the cheapest discs on the market, but they are very reasonable. Verbatim are nearly twice the price for the same performance.