M2 cards aren't the same as the Ps Vita memory. Ps Vita memory is proprietary, meaning it only works in a PS Vita or the PSTV.
You do NOT need a sd2vita if you have proprietary Ps Vita memory. The sd2vita is only a cheaper alternative to the standard Ps Vita memory.
The Ps Vita (proprietary) memory has a maximum capacity of 64gb, with a price-tag usually over $100. You might be asking yourself "Is the Ps vita memory better because it's more expensive?". No, the Ps Vita 64gb units have many reports of them quitting or "burning out". IMO a Samsung MicroSD is 100 times more reliable, also with the SD2VITA you can use a 128gb/256gb microSD.
I'm going to do a price check based on US retailers from eBay.
Samsung EVO PLUS 64gb MicroSD = $23 USD
SD2VITA 3.0 Red Text/Revised Version = $13 USD
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64gb Proprietary Ps Vita Memory = $95USD
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$36 is cheaper than $95, this is the main reason why everyone wants one.