Theres more variety in saltwater,fish,inverts,corals and all.Freshies have a tendencie to be a little more drab in the color dept. but as far as personality,for fish,I'd say its a dead heat.Predators Hmmmmm, Id say that saltwater predators have a little more specalization,More of a niche factor,were as fresh water really dosnt get that as much.Its a judgement call.I really dont think that salt is anymore difficult to keep than fresh,if anything its the other way around.Saltwater tends to be more stable and more flexible as far as how many types of filtration set-ups you can use.Fresh water is much more limiting as far as that goes,its either wet/dry,hang-on,or canister and small variations on these,but relativley the same.Salt are a bit more on the pricey side this is true,but if you shop smart you can keep the cost down.What ever you do,DO YOUR RESEARCH on every aspect of the system from live stock to substrate to filtration to lighting.The more research you do the better you will understand your system,the better you understand your system the more success you will have.