If you're concerned about speed, use portsnap. It's now in the default installation and is the suggested way to update your tree. In saying that, csup and cvsup still essentially do the same thing and there's nothing wrong with using either method.
Thank you for the response and the suggestion. So even the performance issue may be solved, still, can some ports be excluded from being upgraded in a relatively trivial way?
Hello. portsnap can have something called a refuse directive. Though it is not recommended as some ports require other ports as dependencies.
portsnap is more secure and faster than the old way of cvsup. It also works with timestamp and only downloads ports that have changed since last usage.