Same thing, They just make up names to confuse people, I think.
As for the holes, number of coils, etc. That's kind of a personal preference, there's no real right answer. I prefer 2ohm, single coil, double hole cartos. That matches my
vaping style and my various setups I have. YMMV, if you are using a very thick juce it would be a good idea to get a 3rd hole. If you are using a fixed voltage device, and 2ohm cartos don't perform well enough for your tastes, you could go to a 1.5ohm single coil for a hotter fuller vape. Alternatively you could go the opposite route if a 2ohm is too hot for you.
I'd really suggest getting a few cartos of different configurations so you can figure out what works best for you, assuming your budget allows of course. I bought most of my UDCTs from Madvapes (where they call it the Artemas) Madvapes is a well respected, popular vendor so no worries with them.
Hope this helps!