The K-01 UHS-1 compliance is noted on the spec sheet on the
Pentax Imaging USA website under media storage.
UHS-1 support is important. Both SDHC and SDXC cards can be UHS-1 compliant which has a potential performance up to 104MB/sec. The SD Card Association has this
roadmap for UHS. There is already UHS-II in the pipeline that will have a bus speed capacity up to 312MB/s.
This is all essential for better video quality. SDXC is using exFat file format which allows for cards larger than 32GB and file sizes bigger than 4GB which is needed to increase the length of continuous video clips. Here is the
capacity page at the SD Card Association. The K-5 is not UHS compliant but it can use both SDHC and SDXC cards.
One question if you use an SDXC card in a K-5 is the card formatted as exFAT? If so is there a performance difference using an exFAT formatted SDXC card over a FAT32 formatted SDHC card in the K-5?
I think the faster bus speeds of UHS should help with better power consumption too.