What Memory Card or micro SD Card is best for 4K camera Samsung NX1 and Lumix DMC-G7?

Hi,

I purchased Samsung NX1 and Lumix G7 both are 4K

I want to buy micro SD card rather than memory card so that same card I can use in my smartphone also (so I will be using adapter with micro SD in Camera).

I don’t know what card speed i will require, if I shoot 4K with highest frame rate, I am assuming camera in-memory/RAM is not enough to hold continues 4K video shoot data and require fast memory on which RAM data can be parallel transfer to Memory Card while shooting.

I know all these terms like U3 or UHS or Class 10, as I already read here http://www.bhphotovideo.com/explora/phot… > )

But even though there is one confusion among different range available in market, when we see their Prices at bhphotovideo:
Example:

Lexar 32GB Professional UHS-II 1000x microSDHC Memory Card (Class 10, U3) at $32.95
This says: 150 MB/s write and

Lexar 32GB Professional 1000x UHS-II SDHC Memory Card (Class 10, UHS Speed Class 3) $26.95
this says: Max. Read Speed: 150 MB/s

SanDisk 32GB Extreme PRO SDHC UHS-II Memory Card at $74.95
this says Max. Read Speed: 280 MB/s and Max. Write Speed: 250 MB/s

now you can observe that both are UHS-II, Class 10, U3 but there is major difference in price
whatever speed they are claiming are not ‘sustained transfers speed’ but it is maximum burst speed of a card
so why there is major difference between price? And which one should I buy?
Added (1). If we observe only UHS â€Â" I or UNS â€Â" II (which is max burst speed) and U3 (30MB guaranteed lowest speed) then all are same but still I can observe some card are more expensive with same specification but they have mention 280MB/s Read and 250 MB/s Write speed that is actually burst speed so if a card is UHS-II that mean 312MB is max burst speed that what is the use of telling customer with different speed eg 95MB/s or 150MB/s or 250MB/s.
Added (2). See one more example:
SanDisk 32GB Extreme UHS-I microSDHC Memory Card (U3/Class 10) $19.99
this says: Max. Read Speed: 90 MB/s and Max. Write Speed: 40 MB/s

SanDisk 32GB Extreme UHS-I SDHC Memory Card (U3, 2-Pack) $68.95
This is 2-Pack so let’s divide $68.95 by 2 which is $34.47
this says: Max. Read Speed: 80MB/s and Max. Write Speed: 60MB/s

both are from SanDisk both have same UHS-I, U3/Class10 but one is 19.99$ and other is 34.47$
Added (3). I also want to know If I don’t use any memory card then will my Wi-Fi in the camera can transfer 4K data with highest frame rate in real time (what I means is Wi-Fi coming in camera has that much speed/bandwidth to transfer 4K data in real time to external Wi-Fi storage.) and what is actual transfer/write speed require for 4K video with highest frame rate?

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