A:AnswerEverything really depends on what you want to use them for. All claims of speed by mfr's and retailers are questionable as marketing hype. My wife and I recently purchased these cards for our phones. We didn't really check the Read speed, but my initial Write testing using a USB3.0 card reader on my desktop system capped the write speed at about 30MBs. However, that 30MBs is ONLY with a single large (4GB) file being copied and written sequentially. Writing a large group (2000) of small files (average 5MB each) to these cards brings the write speed to a crawl. (Note: It took just over 5 hours to write 90GB of data (music & photos) to the cards.
Note: These cards come preformatted as exFat. Unfortunately, due to our phone limitations, we had to reformat them to fat32 (which slows them further). However, after reformatting, these cards work with our phones and record video and photos with no problems (so far).
In my experience over the last thirty years with computers and photography I have tried numerous mfr's cards. My favorite/recent/current fastest (but yet not ridiculously expensive) is the SanDisk, UHS-3, Extreme-Pro. Even when copying large groups of small files it maintains higher speeds. You will definitely pay more for them. So the question is - do you want speed (buy the Extreme-Pro), or do you want high capacity, at a low price (buy these)?
If you are a professional photographer shooting high speed (10fps) 20Mpx photos these are not the cards for you. But, if you are a pro you wouldn't be asking this question. So I am assuming you are the average user who wants a high capacity card, for a phone, or maybe point and shoot camera, I say go for it you won't be disappointed.
