I've read that Trascend and Sandisk are highly recommended "for general usage", and I haven't read about a particular brand nor a particular size not working with Gateway (except for some defective Kingston cards).
From the 4 you have mentioned, I think you could go for 2 MicroSD of Samsung, a 32GB MicroSD is proportionally cheaper against a 16GB one, but you should also check the prices to see which is better for you.
A SD card (which is generally more expensive than a MicroSD) will probably not offer any benefits over a MicroSD with an adapter. Two users helped me testing the load speeds of emuNAND with a fast SD and a normal Class 10 MicroSD with a SD adapter, and the difference was really minimal.
If this helps, I just bought a pair of these:
http://articulo.mercadolibre.com.mx...-sd-xc-clase-10-mobile-ultra-android-30mb-_JM for a relative good price, 30USD for each.
30USD sounds kinda like a rip-off to me considering you could get the same card for much less :
http://www.ebay.com/itm/SanDisk-32GB-32G-Ultra-Micro-SDHC-SD-Card-UHS-I-Class-10-MicroSD-Memory-Adapter-/251413332644?pt=ES_Teléfonos_móviles&hash=item3a896702a4
If it's even the same card lol.
Yeah, from a person with minus 1 points, way to go...

yes i don't sre any reason it should'nt work.In theory could a 64GB Sandisk class 10 card be used for the multirom if formatted with FAT32?
Is it an Ultra Class card?I use the 16GB version of that Sandisk in mine. Works fine.
Doesn't matter. It's just a speed rating.Is it an Ultra Class card?
But there are class 10 cards and ultra class 10. There must be a difference...
Class 10 and UHS-1 actually mean the same thing in practice: minimum 10 MB/s sustained for both read and write. UHS-1 specifies a higher bus speed, but it's all backward compatible.But there are class 10 cards and ultra class 10. There must be a difference...