With either format you will have a near 100% success rate reading them in any DVD-ROM or -R/+R recorder. The compatability issues show up when it comes to reading those discs in set-top DVD players, i.e., the ones attached to your TV's for playing movies. I think that the -R have had a little better compatability with set-top players so far, but +R have been closing that gap and with Pioneer supporting both formats in their new model (they developed the -R format) the writing is on the wall. +R will become the dominant format until we move to Blu-Ray, but either is fine.
FWIW I've got the Pioneer A04 model (one of the, if not the first of their DVD-Burners). It is a -R model and I have never found a DVD-ROM or Set-top player that wouldn't play my burned discs.
Oh yeah.... -R media is significantly less expensive right now.