SanDisk (they invented the technology) and Samsung are the only manufacturers of the chips used in the cards, so they're both going to be using the best chips in their own cards.
I find SanDisk a pleasure to work with (I've had to contact them a few times - not about bad cards, the only bad SanDisk card I've had in over 20 years is one I broke by mishandling). 5 year warranty on their cheapest cards, and all you do is fill out a web page to get a replacement if the card goes bad. (Or you can do a live chat with a tech from their site. They answer their emails quickly too.) I've had to deal with Samsung on other matters, and I'd rather deal with SanDisk. The cards may cost a few dollars more, but it's worth it. (Make sure you aren't buying counterfeit cards - a $20 128GB Ultra card on eBay probably isn't - either Ultra or 128GB. It's trivial to reprogram a card to say it's larger than it is, and with laser printers it;s just as trivial o counterfeit the look of the card - and the package. Buy from a known and trusted source.)
Here, let me make this easier. Which one is better for me and why?
1. Lexar High-Performance MicroSDXC 633x 128GB UHS-I/U3 (Up to 95MB/s Read) w/USB 3.0 Reader Flash Memory Card LSDMI128BBNL633R
Or
2. Samsung 128GB EVO Micro SDXC up to 48MB/s with Adapter (MB-MP128DA/AM)
For what it's worth, I just benchmarked both a Samsung Evo 64GB U1 card and a SanDisk Extreme Pro 64GB U3 card in my Note 4 using A1 SD benchmarking app and the U3 card trounced the U1 posting 85MB/s read and 53MB/s write speeds vs 43MB/s and 21MB/s.A U3 card will only outperform a U1 card if you're recording 4k video. The U3 card will be read from and written to as fast as the phone decides - which, except in the case of 4k video, is U1 speeds. (It's like driving a Porsche on a rocky dirt road. An old VW bus will go just as fast.)
Persojnally I prefer SanDisk - I've delt with a few companies over the decades, and SanDisk is a pleasure to deal with.
Radiohawk, I hope you went to SanDisk Online RMA Request and had your bad cards replaced.
How would you compare the SanDisk Pro U3 to the other 3 I listed, especially the Lexar?
A U3 card will only outperform a U1 card if you're recording 4k video. The U3 card will be read from and written to as fast as the phone decides - which, except in the case of 4k video, is U1 speeds. (It's like driving a Porsche on a rocky dirt road. An old VW bus will go just as fast.)
Persojnally I prefer SanDisk - I've delt with a few companies over the decades, and SanDisk is a pleasure to deal with.
Radiohawk, I hope you went to SanDisk Online RMA Request and had your bad cards replaced.
What app are you guys using to test the read and write speed.