They are just a different types of media. No one is better than the other. Some burners use -r, some +r, or both. -r is more widely used and supported though and +r media can cost ya a little more. If you have a v1-v4 ps2 stick to -r. If you have a v5 or higher either will do. If you don't know what version ps2 you have you can check
here Also check to see what formats your dvd player supports, that is if you are using something besides your ps2 for dvd movies,
here