body { .container; }
body > header { .page-header;
p { .lead; }
}
etc
Then you can make use of bootstrap's variables as well for customizing? Obviously personal preference LESS vs SASS, but no reason you _need_ to switch from the default
For large/complex sites, you should take into consideration the performance of various selectors. ID selectors are always fastest, and single classes are faster than complex selectors.
Nested rules in LESS/SASS make things easier to manage, but when you end up using extend blocks, nested files, and parent rules, you can end up with very non-performant CSS rules. It may not matter much in a small page, but on larger pages with thousands of DOM nodes it can add up.
Then you can make use of bootstrap's variables as well for customizing? Obviously personal preference LESS vs SASS, but no reason you _need_ to switch from the default