Especially for HCl, there can be a lot of error just in the initial concentration of acid in your concentrated solution. It is always best to titrate your solution after diluting it. You can buy very accurate NaOH solutions to titrate against, or make your own - if you are very careful to avoid letting your NaOH absorb water, it is much easier to get an accurate weight of NaOH than it is to get an accurate measurement by volume of a concentrated HCl solution.
Of course, that all depends on how much accuracy you need. In many cases, plus or minus twenty percent is close enough, and you can get that even being pretty sloppy. In other cases, plus or minus 1 percent is too much error, and you must take great care in preparing and standardizing your solutions.