It can be hard to tell them apart but the main (and often only) tell is the arms. Extremely long is bad to go in with Bettas.
Personally with a Betta I would try to stick to Bee shrimp. I love my ghosties but I find the Betta ignores Bees but chases ghosts. My Bees also tend to stick to the bottom of the tank or hide in plants, my ghosties swim everywhere which annoys my Betta.
Bees are also mainly vegitarian and love bottom feeder veggie tabs which bettas will sometimes ignore. This makes it a little easier to feed them.
The other advantage to Bees is that they are smaller so there is a lower chance of a Betta choking on them.
The downside to Bees is that they can be hard to find and often cost several dollars more than a ghost shrimp.