Well I just got the Transcend because it's the "faster" card, but I haven't got my EZ-Flash Vi yet to test it on! (Praying that DX get stock on the 20th May!!!)

It has "lifetime warranty" and coupled with Class 6 speed, it was a no brainer for me.

Anyway pretty sure (99.9999%) that they both work fine. .

 

A simple advice here. Don't buy your microSD at DX. They mainly sell fake microSD cards.
Choosing between a kingston class 4 or a Transcend class 6, i will take the kingston.
Classes on microSD cards indicate the write speed which is very low on every flashcarts i know (max 1.7MB/s).
So it's not a trustable value.
Access time to reach data is very important. Kingston SDHC card are mainly Japan made cards (manufacturer Toshiba) which has a really good random access time .

To conclude, i'm pretty sure both will work on EZVi because when a card has a bad acces time to reach data the hybrid mode do his job so your games will start.