The mediacode on a DVD media, you can find it out by using tools like DVD.Identifier or DVDInfo.
The Ritek/Ridata/Memorex/Nashua/whateverCHEAPdlMEDIA can normally be burnt with DL capable burners but most times their mediacode with specific write-strategy is not integrated in the firmwares and also the quality of the media is just not good (enough).
For Verbatim DL media counts the opposite.
For DL media counts even more what counts for SL DVD media too: Buy cheap media and you will pay twice in the end…
DVD-R DL is not that long on the market yet than DVD+R DL is.