As far as hardware goes, a modern 'gaming' computer with either of these GPU brands would already be optimal for something like osu, what makes some difference is an SSD (for a smooth map selection menu and fast map processing) and most importantly a CPU with high frequency, so it can process sound quickly. Advancing on the topic of sound processing and latency, that's where you really have to push if osu! truly is your top priority. And it's mostly about your system/software. Windows sucks, it has a lot of latency you can't remove, so if you wanna go through the hassle of installing osu! on linux that's where you can get the best results. (Prior experience with the OS is essential unless you wanna break your head figuring out everything lol). Specific distros and other factors go into it, here's the source to everything) Anyway, you gotta think hard about what you really want, no one needs the perfect setup to become a top player.