Hi and welcome here @ CDF,
most new home DVD player are able to play +R and -R and most players are also capable to handle DVD+R DL when the booktype is changed to DVD-ROM.
The DVD-R DL format is comming but there are only a few burners available that can handle tis format, i can't tell you nothing about the compatibility to stanalone player.
You can't say which format is the best, but +R has advantages because of the fact that you can change the booktype to DVD-ROM which is necessary when you have an older DVD - player that is not able to play +/-R.
When the burner is able to change the booktype then I would prefer +R.
DVD+R DL has the advantage that you can store up to 8.5GB on the disk, good when you want to backup movies without a loss of quality incl. all extras. But the medias are expensive.