That question has been amply discussed. Here is my *personal* take on it:
Scart RGB is, potentially, closer to both the source (the output of the MPEG decoder is RGB) and the display (what you see on the display is RGB). However, it has caveats:
1. SCART is probably the worst connection ever invented. Keeping a true 75 ohm impedance matching on both connector and cabling is almost impossible; the pins don't make proper contact in most of the times. SCART is a good example of convenience over quality and good engineering.
2. RGB takes a lot of bandwidth. This, along with the fact that SCART connectors and cabling are poor and not properly matched makes it almost impossible not to loose a LOT of signal in the path.
3. A lot of modern DVD players, and, above all, displays are designed in a way they, in some point, do a RGB<->YUV conversion, mainly because in the US SCART does not exist. So it's quite possible that even if you are feeding your TV RGB, it is being translated into YUV and then back into RGB.
4. SCART RGB is always interlaced. So it makes the deinterlacer useless.
YPrPb, on the other hand uses Phono or, better yet, BNC connectors. They provide much better impedance matching, and, better yet, they allow you to use true 75 ohm coax cabling. The provide better contact. And usually both on the player and on the display side, everything is gold plated, avoiding oxidation. It also requires much less bandwidth, and, hence, it's less prone to loss anyway.
Internally, I have no doubts that RGB is a better way to transmit a signal. However, the moment you want to get it out of the player, YPrPb is a much more adequate means of transmitting it.
As an Electronics Engineer, I have no doubts that YPrPb is a much better designed standard. I can fully understand why the US has never adopted SCART and has, instead, adopted YPrPb.
Also, if SCART RGB is better, what's the point of including DCDi and DCC (both of which only work with YPrPb) and making such a fuss about it?
Knowing some people at Philips, I guess that there may have been one very simple reason for that statement: that it is a "legacy" statement, something that was put in when Philips DVD Players didn't have YPrPb outputs, so they were comparing with S-Video and Composite.