This is a perfect line of reasoning, assuming: a) your ISP can competently run a secure DNS service correctly (latency is not the whole story of 'performance')

This is a perfect line of reasoning, assuming: a) your ISP can competently run a secure DNS service correctly (latency is not the whole story of 'performance') b) it's acting entirely in your interests and not attempting to hijack your DNS service to insert ads etc. Personally, I've had ISPs where neither of these things have been true.