Either round will work well within the 40 yards you stated. You have already stated the need for a head shot which in my opinion is exactly what you need to do when using a .22lr. However you mention that you chose that round due to the "reduced potential for collateral damage". Make no mistake a .22lr will cause damage and in some cases penetrate walls depending on range.
"Si vis pacem, para bellum". If you want peace, Prepare for war!!!!