We've traveled extensively with our boards. James' board in particular is glassed light and doesn't travel well. For airline travel we use a hard case - designed for a half board. I swear by hard cases for travel.
For day trips on the boat, I prefer a sock...easy to slip on and off. I HATE zippers! I find they scar finishes and they typically don't allow enough slack in the sides to allow the fins to remain attach to the board. Who's going to take the fins out between rides?
That said...enough "slack" on the open end to allow fins to slide in still attached to the board. Draw string or elastic on the open end. Quilted fabric for extra padding and a light color to NOT absorb heat.
I don't like the carrying straps and handles. Like I said, I use a hard case for travel, for in the boat I just want surface/ding protection. The furthest distance I'm carrying is the rear locker to the back of the shop - 3 feet
An eyelet on the top of the bag so that I can hang it to dry - the sock will get wet and I leave my boards and the sock out to try.
$50 is too pricey, I want one for each board - especially my exceptional artwork masterpieces!
I won't spend $300 for 6 of 'em. $20? I'd buy those.