I've tried Philips vision plus and Osram's Silver stars, and found them both a worthwhile upgrade, and the Osram's were the slightly better of the two.
thanks CC, why were the osrams better?
Sorry for the delay in answering you 2007, I can only say they had a whiter crisper light when compared to the Phillip's, that's not to say the Phillips were not good, because they are, just the Osrams a bit better IMO.
You made the right choice.

Are you changing all four, or just the dipped.