YV12 makes more sense than YUY2 since your footage already is YV12 to begin with and it will make you save space.
Also, Alan got it slightly wrong: ULRG (the first one) is RGB24 and not RGB32, as RGB32 and RGBA are the same thing (and thus you can say that ULRA is RGB32, instead). The difference between the two colorspaces is the presence (or lack) of the alpha (the transparency) channel, which you do not have in RGB24 but have in RGB32. If you want a simple way to keep in mind which is which, here's why they are named like that: the numbers come from the fact that they are 8bpc (8 bit per channel) colorspaces, which means that for every colour on every pixel you have 8 bit. RGB24 just has red, green, and blue, so that's 8*3=24. RGB32 has red, green, blue, and alpha, so that's 8*4=32.