200 because I'm lazy and don't feel like changing filter socks more than needed. Lol and mesh doesn't capture enough to polish the water to sparkly goodness.
I use 200 since I get annoyed with having to change and wash filter socks too often if I use anything smaller. I hated mesh socks since I would get crud all over the sump when I used them.
Where do you buy 150 and 300 micron size socks at? I've never seen those micron sizes before.