I recently bought a Kingmax 16GB Class6 microSD card. While I was initially transferring my files from my Sandisk 8GB Class2 microSD card, I noticed that the transfer rate was kind of slow, so I decided to do some benchmarking.
Software: CrystalDiskMark 3.0
3 different microSD cards using same USB card reader
Card #1 - Sandisk 8GB C2
Card #2 - Kingston 8GB C4
Card #3 - Kingmax 16GB C6 (new one that I just bought)
Here are the results (Seq Read; Seq Write; Random Read; Random Write):
Card #1: 17.08MB/s; 5.13MB/s; 17.09MB/s; 1.05MB/s
Card #2: 17.23MB/s; 9.53MB/s; 17.23MB/s; 1.92MB/s
Card #3: 16.05MB/s; 5.22MB/s; 16.73MB/s; 1.02MB/s
Summary: My new Class6 card was about the same speed as my Class2 card.
I approached the vendor and they tested a few other Kingmax card that they had in stock... all cards were reportedly about the same speed as the one they sent me. They swear that it's not fake. Maybe its a bad batch of cards but somthing is weird/wrong. Anyways... I'm sending my card back for a refund. I am going to stick to my Kingston Class4 card now.