v7's +R typically good, small share of failures with +R--same can be said for -R. It is best to get a dual format drive if you have a post v5 PS2. This way if one format fails, you can easily move to the other.
v5's about 50/50 success rate with +R--works good on more mint condition machines, but ones that have seen a lot of abuse don't like +R that much. -R is stable across the field here. A -R capable drive is your best bet. Quality of media really begins to come into play here, and becomes more important as the PS2 goes further back in revisions. Quality DVD-RW can often be used from here up. Frequent quick erasing will sometimes not allow a good burn though. Full erase should be done periodically on DVD-RW's if used.
Pre v5's are firmware dependent for the +R support. This is basically a production date issue for the laser units. -R is the best choice for these units. Again -R capable drive should be used here, and cheap media should be avoided (ie Princo's). RW is not typically viable on these machines either.
If it ain't broke don't try to fix it! But, hell if you can tweak that bastard just a little bit more....hehehe.