It seems that in general the dual format drives perform better on one format or the other, so you might check around or do some tests. That is, they burn both formats but speeds may be lower on one than the other.
For anyone choosing a format more generally, be sure to read the discussion below the Spath article, that article is not particularly useful as a guide to choosing a format. For that purpose, it's needlessly complex, and emphasizes factors that are either somewhat hypothetical or just don't apply to most users of write-once (vs. RW) media.
There really is not a simple answer. +R has some advantages for data, especially if you do a lot of incremental backups. It has the advantage of coming out later, so being somewhat more up to date technically. But that also means there's less of an installed base right now.
Price and compatibility are real world factors, aside from the technical aspects. For Europeans, at the moment, -R seems to fare better on those two counts. For those in North America, +R might get the nod (because the price and compatibility gap is smaller, and the format is likely to grow much more rapidly than -R).
So as with all this stuff, it depends on your own situation. Where you're located, what you're using it for, and whether you're thinking about the long term or not.