Now that mediawiki supports svg with png fallback for logo's, we should use svg over high density logo's.
to switch, it's as easy as doing
$wgLogo = 'png_image', (optional) $wgLogoHD = [ 'svg' => 'svg_image', ];
or for mw-configuation
'wgLogo' => [ 'enwiki' => '.png', ]; 'wgLogoHD' => [ 'enwiki' => [ 'svg' => '.svg' ], ];
before deleting the 1.5 and 2.x images wait a couple of days.