One point: the whole URL doesn't get sent to the DNS server, just the domain name.
Regarding privacy, Cloudflare are at least saying they aren't spying on you. Your ISP may not even be saying this. Also, Cloudflare don't necessarily have access to your name and address, whereas your ISP does. Also, many different sites can be hosted on the same IP address, so merely tracking the IP addresses a client is connected to won't necessarily tell you what sites they're visiting.
Regarding privacy, Cloudflare are at least saying they aren't spying on you. Your ISP may not even be saying this. Also, Cloudflare don't necessarily have access to your name and address, whereas your ISP does. Also, many different sites can be hosted on the same IP address, so merely tracking the IP addresses a client is connected to won't necessarily tell you what sites they're visiting.