<p>NaBH4 doesn’t do crap to either esters (no reaction at all) or carboxylic acids (simply deprotonates)</p>
<p>LAH does though, to carboxylic acids it will generate the dianion and then the O2- will leave forming an aldehyde, which then gets further attacked by H-; then for esters, it will attack and then kick out the OR leaving group, which generates another aldehyde and gets attacked again.</p>