Did I post my round up of all the Discmania discs in this thread? I need to find it, it could be handy at times...
Aaaanyway, the MD2 flies pretty differently according to the plastic. The C and some S-Lines are pretty much a Mako-shaped, speed and glide Buzzz, the S-Lines vary a bit though. The P-MD2 is for me the straightest disc I've ever thrown, doesn't turn on a full rip and only fades a couple of feet, unless I give it nose up. Fast, glidey, reliable, will work any line I want them to. The ION is my bread, the P-MD2 is my butter. They're forgiving to form issues (unlike a Comet for example), but they're not terrific in the wind. Also, everyone else will disagree with me on this.
The SG-MD1 is my wind beater. I can rip it into any wind and trust it to fly straight. In calmer conditions it fades reliably. The S-MD1s are just as stable/overstable, the Ds often start out more stable (but then again sometimes not), but they're the most OAT unfriendly disc I've ever seen. Even though they can take heavy headwinds easily, you just have to give them a tiny bit of OAT and they'll flip out completely. They feel weird in my hands, and that leads to bad releases. The SG-MD1s on the other hand can handle much more OAT, and feel better in my hand due to the gummyness.
IMHO Discmania flight ratings should be ignored. If you just go by them every mid they produce should fly the same...