open headphones tend to have a bigger soundstage (more 3d-ish sound) than closed headphones do.
open headphones also leak sound out and you can hear everything around you.
closed headphones tend to have slightly more immersive or warmer sound.
closed headphones also tend to be a bit hot and you need to take them off every once in awhile or your ears will sweat.
as far as ohms is concerned. no, less is not always better.
headphones around 30-50ohm normally can be driven easily by portable devices like ipods, phones and laptops and most soundcards as well.
headphones around 150ohm might have trouble on portable devices without a portable amp but might be okay on decent soundcards or integrated sound.
your heapdhone sensitivity matters here and affects how easy they are to power.
while certainly not always true, higher ohm headphones sometimes sound better. for instance in a direct comparision between dt770 32/80/250ohm versions the highest ohm is also the hardest hitting and best sounding amongst them. but, its not as simple as that in most cases.
for the price of the units you are looking at... you might be better suited using a modmice to attach to the side of a nice pair of studio headphones. but your choice. perhaps some sennheiser 598 or even better some beyerdynamic dt880. the modmic normally costs about $30 if i remember and gets good reviews.