SDXC card speeds

I have an iMac (Retina 5K, 27-inch, Late 2014).

I am using the built-in SD card reader to transfer files from a micro SDXC card (with a microSD to SD adapter) which I use with my Sony Handycam.

It takes rather long to read the files from the SDXC card. It can easily take upwards of half an hour to read the data from the 64 GB card. The type of card is: SanDISK UHS-I / U1 / Class 10.

I'm thinking to buy a faster card, like a SanDISK USH-I/ U3 / Class 10.

Any suggestions on whether this will actually increase the data transfer rate to my iMac?

Or do I need to go up to a more expensive UHS-II card to get a better speed?

Or is this throwing away money and not going to increase file transfer speed at all?

Thank you!