If you scrap a laptop you get a nice, auditable, chain of custody from the end user to the company that will certify it's been destroyed. If you sell someone their old laptop you need to ensure that it's actually been wiped, not just "I copied my files over and started using the new one". I've seen a few IT departments be not great at "Sam got their new laptop two weeks ago, someone should follow up now to see if the wipe on the old one happened".

One choice won't get you fired, the other might save you a bit of cash.