Really depends on what you're using the proxy for. There is such a thing as BIS when it comes to proxies, I'd say.
Usually for speed and stability, you can pick up datacenter or ISP/static proxies. Although, if you're using multiple accounts and longevity is what you're after, a lot more comes down to IP reputation and quality, which reliably comes from residential or mobile proxies. Generally though, you can find some really fast residential/mobile options, especially the unlimited data ones, and I use these proxies the most considering what I need them for. They are far more expensive than the other options proxies to be sure though.