This question being asked - and mostly the matter being discussed - is less about how different brands compare with each other than how different types of quality tiers of tire compare. Nobody in here is saying that you're an idiot if you run Vittoria-branded tires. When people are saying "GP5000 is a noticeable improvement", they're saying it's a noticeable improvement over Conti's entry-level tires (since that's what the OP asked about), not that it makes Corsa Speeds look like garden hoses or whatever.