the cobra sleeving comes in different sizes and is uv reflective so will look better in the case...
the difference in the 2 products is the width of the layer the black is thicker and potentially harder wearing. but the cobra looks so much nicer. especially if you get it to match or clash with your led's.
there is no real difference other than a personal choice. me i would go for the cobra over the black... you may not want to if your case is particularly dusty as them cable ties will look grubby very quickly.
How will you sleeve the cables and in particular the 24-pin? Will remove all wires from the connectors? 1/8" might work for smaller cables, but you probably need 1/2" or 5/8" for the 24-pin cable. The smaller the sleeving, the more difficult the task will be.
I checked a couple Antec cables that use the following sleeving size:
6 and 8-pin cables: 3/8"
small cables: 3/16"