Is Restrict Access server behavior faster than .htaccess control?

My site uses cookies that are set from the login page to pass values to the next page's url links and to the text. Visitors must login or they won't have the cookies available to them.

Since it is recommended to put Restrict Access on every page it seems to me that that will slow down server response time. My potential solution is to use .htaccess, instead of Restrict Access SB to force visitors through the Login page. BUT, since deploying .htaccess means that it must search through every sub-folder to see if an .htaccess file is deployed in them too, that must also slow down server response time even if there is no .htaccess file anywhere down in the sub-folder structure.

So, am I right that using Restrict Access server behaviors on a big site slows down server response time, or is that server behavior simply passing the MM_Username etc, on to the next page in a manner that the subsequent page doesn't need to check with the server beyond dishing up the page with the cookie info in it?

...and, is there a way to tell .htaccess to restrict its search to only the top level folder?

Comparing these two tools, which would you choose and why?

As always, thanks for your help!