Yeah, they really do. Fact is I have tried a lot of very good discs in the past. I have an amazing beat to perfection S PD in my bag, a sweet super straight flying DX Teebird, a beat Star Leopard that feels like it's the extension of my left arm (I'm LH) and a few ESP Buzzz that I can lazer at baskets. Off course, of all the discs I just mentioned ,only the Buzzzes were easily replaceable, the others were like small treasures that I could probably not replicate easily.
However, now that I think about it, I believe I wasn't just after consistency, but after some unity as well. To me, I like the idea of having a bag filled with one brand of unique discs that I know are great performer, and were thoughtfully designed. I'm eager to set up my new MVP bag for that. It seems like having a mostly** MVP bag will help me stop my desire to buy every discs that are produced from the different company.
** For now, I still carry Magic/Wizards and probably a speed 10-12 or two in the bag.