You might well see an improvement in downloading speeds with a faster card. For me it is a non issue, because even with a few hundred large raw files to download I can still only view/edit them a few at a time and it takes Lightroom quite a while to keep up and render previews ready for viewing.
When I made my purchase decision, a few years ago, my cards were around £55 each and it was a tradeoff between capacity or speed. I chose capacity. Nowadays you can have both for not a lot of money, relatively speaking.