When I did my bus, you almost had me convinced to do steel. I like a lot of the "Pros" like:
No rivets - smooth side
Simple weld on - no pre-heat
work the metal just like automotive body work
But, there are some "Cons" too.
Weld spots visible from outside (lots of sanding)
But, there are some nice "Pros" to the aluminum
Easy to handle
Easy to form and cut
Same look and material as the bus builders used
"Everyone Else is doing it"
The "Con" of aluminum is limited only to the potential of waving. And if installed hot, and we stay out of AZ, that should'nt be a problem.
Also, be sure (this could be a pro for steel), that you protect your steel structure from the aluminum.
Cliff is a genius in my 31 year old opinion, so this isn't to contradict him, just sharing my experience
I'm with Scott - this is a rare experience, so I'm having fun!
One additional thought: If I was replacing the lower aluminum, and the aluminum around the windows, then I think the smooth side steel might be the way to go. You could spot weld the whole thing and even smooth seams if necessary (just like auto body work). Hmmm, maybe I should have done that...