I have a Palembang/humpback puffer with I have in a 30 gallon tank. He is very aggressive towards other fish. I do have 1 full grown bristle nose pleco that he doesn't bother. He is about 4.5" long now, and the articles that I have read say they get to be about 8", but I have never seen on get that big. They live to be over 10 years old. They don't move around that much durring the day. THey are a "lurker" fish, so he just moves around durring feeding time, and at night when he is out on the prowle for food. I feed him every other day, and feed him shrimp. About once a month I will feed him live fish, but after quaranteen for about a week. The one time I didn't quaranteen he got a fungus on his body.
The Arrowhead puffer was going to be my first puffer I was going to get, the only problem was I couldn't get one from the LFS. They are about the same as the Palembang/humpback. The only big difference is that the arrowhead will need about 4-5" of substraight for them to burrow in. The arrowhead is a lurker fish too, so he will not be real active. They look really cool burrowed in the sand and snap up when a fish swims in front of it.
If I was to do it all over again, and could get either of these fish I would deffenitly go with the arrowhead. Although both are a great choice. Just remember if you are looking for a fish that will be moving around a lot and can get tankmates for, then you are looking at the wrong fish. Most if not all fresh water puffers should be kept alone, or with same spieces of fish, and even some can't tolerate that. Good luck and let me know what you decide on.