The most significant difference IMO is the distribution model. An iPhone user will have one place to look for new apps: the Apps Store. Whatever app s/he is looking for, it will be there or not be at all. That's a huge advantage for a software developer. An advantage the Palm didn't have.
Also: sure, in 8 years the iPhone may be dead and Apple bankrupt, but (1) do you really think so? and (2) do you really need to plan that far in advance?
Also: sure, in 8 years the iPhone may be dead and Apple bankrupt, but (1) do you really think so? and (2) do you really need to plan that far in advance?