Species of octos and cuttles vary in difficulty.
Ive kept both of various species and would say in my opinion that octos are easier.
Things to worry about..
octos
-Escape proofing the tank
-Will eat most cleanup crew (snails and hermits)
-If its a shy one, they will be harder to find in the tank
Cuttles (Most likely if you get one, it will be a bandensis)
-Require more food and very difficult to teach it to eat frozen. (This makes cuttle keeping very costly if you cant catch your own food)
-Seem more intolerant of water quality thats anything other then perfect
-Shorter life span. (From an egg, the longest ive had one is 11 months. Many start dropping off even at 6-8 months)
-Bandensis if found available usually come as eggs, so this requires specific live foods and great care to raise them from that age.
I hope this helps! Most ceph keepers start out with an octopus such as a bimac.
You can check out my eperiences at
http://thetentacleparadox.com/CuttleFarmArmy-About.htm