I didn't even think to check the minimum requirements for the Micro SD cards for the P3... Looks like all the ones I've been using for my P2 are all class 4...
Guess I'll need to buy a bunch of new ones “Class 10 or UHS-1 rating required”.
These cards are essentially all the same (minus the write speed). The important specs are 64GB in size and class 10.
If you are getting a Phantom 3 Professional, then it would be a good idea to get the card with the fastest write speed for shooting video in 4k. That would be this one at 90MB/s:
sorry I did not see this John, I purchased the fastest one I could find but have to admit I am not sure how much of a difference it makes. The card I show dropped in price by about $30 US in three weeks.