keep in mind you
CAN customize your iPhone if you know how.
Also keep in mind that flash is highly overrated and html5 is the new thing anyways.
Also iPhone
does have flash support, and it will only get better as more 3rd party devs continue to improve Apple's products.
A lot of people are going to tell you that the iPhone can't do this or that, when it usually can if you just know how.
It's the same as when android first came out and people were going off about how WM could do so much more, but now it's so obvious that WM has been outmoded by both apple and google.
if you want to know if the iPhone OR android can/can't do something, ask or look up in their respective forums, and I would honestly wait till BOTH devices are out (not fair to compare the Evo to the 3GS...) and test them in store and remember that you can infinitely MOD both devices.
Also keep in mind that android has been fully ported to the iPhone 2G and 3G, and I have no doubt a full port is coming to the HD/4G (both linux based). So keep in mind you can probably be able to dual-boot BOTH OS's from one device, something an android phone could never do (since iPhone OS is not open source)