Overview
I have just received samples of these discs, they both have the same mid and appear to be of identical quality so I will do a combined review
These discs are produced by one of the top manufacturers CMC, using only the top grade dye formula. Looking at the burn side of these discs I can see the quality as I expected.
Currently Dual Layer media is in it's infancy and at the moment [Oct 20] D/L Burners and Media have only been on the market for about 12 months. So make sure you go to your drive manufacturers website and download the latest firmware to take advantage of this new format.

Under The Microscope
The drives we are using in this test are the most common ones most of you are using.
If you are not sure about your drive try and buy a sample disc pack from one of the online retailers or ask your local shop if they can sell them individually just to be sure. Currently DVD+R media is all that is readily available and all the DVD+R D/L burners burn the video as DVD-ROM book format to enable better player compatibility, this is fixed in the drives firmware and cannot be changed.
DVD-R is very slow to hit the streets and I have been fortunate to receive only a few beta test samples which never got into production.

A recording has been made on each of the drives with Nero C D/DVD Speed ISO burn mode and then tested with DVDInfoPro testing software.

If you click on the image of the relevant drive below the graphs will come up in a popup window. TESTLAB DRIVES

Conclusion
Dual Layer recording is difficult to achieve perfection and with any media have used I cannot always be guaranteed to be 100% successful and player compatibility is not good especially with any players over 12 months old. The discs I did burn successfully all played in my latest DVD Players with a slight pause at the layer changeover point and from the graphs produced it can be seen that there is some differences between the layers. The disc image I burnt is 8030megs which is just over 100megs under the maximum size of 8152meg for a Dual Layer disc. I do not recommend trying to burn any more data than this onto the disc as it will render the layer switch too near the outer edge and could easily fail to burn past this point or produce read errors in the burn. Personally I would give the disc some more leeway and limit the file size to 500megs below the maximum.
The burning speed of this media is 2.4x, taking 45mins to burn a full disc, this is somewhat slow by today's standards when some of the drives will burn D/L media at up to 8x speed but at a price premium. The Plextor PX716A was able to burn at 4x speed but I was unable to read it past the layer change (the results can be seen by clicking on the drive image in the popup window) So these discs are unsuitable for Overclocking the burning speed.

Although the error rate is a lot higher than I have come to expect from DVD media most of the burns were within acceptable limits and all played OK on my test DVD player but there was some stuttering & jumping around the layer change area of the discs. If you plan to use Dual Layer recording make sure your player is capable of reading Dual Layer media and I would definitely advise you the ask your supplier for a few samples first. At around £2.00 per disc is 10x the cost of a single layer disc which is going to be more reliable. At £2.00 per disc they are not bad value for money when you can find others at over double this amount. After all when DVD-R media first hit the streets £2.00 was the entry level price. I cannot envisage the price dropping much lower in the foreseeable future.