There is no best format, it depends a lot on your own situation. What you say is not true anymore, there are loads of DVD players that can read both formats and both DVD-R and DVD+R can be used for data storage. Here are some articles that will help you understand both formats:
The DVD format war - Current standings
Why DVD+R(W) is superior to DVD-R(W)
In general I would say, use the format that works best for you. In my case all my DVD players can read both DVD+R and DVD-R so I use both.