Should I get a betta or a crayfish? I am going to be buying a ten gallon tank...?

Well the good thing about crayfish is they ARE indeed really cool. Unfortunately, some of them do die easily, and you have to get specific foods for them. They are also skilled escape artists-I actually had a ten gallon tank with a cover and I watched one launch itself into the latched part of the lid and escape. Its amazing, but inconvenient for when you aren't hom because they die if they escape. Also, they generally are not very friendly and can even pinch-which hurts a LOT. I personally would suggest another beta, which, contrary to popular belief, CAN be housed with other fish such as goldfish. They must be non territorial fish as goldifsh are. I kept one for six and a half years in a tank filled with goldfish, silver dollar fish, zebra tetras, neon tetras, and guppies with no issue. Crayfish tend to be very territorial and will chase fish, I've even seen one kill a rather large goldfish. Whichever you choose, enjoy! Hope this helps :)