Brad,
I am sure you are going to get all sorts of conflicting advice on this
subject. Honestly I think from my experience that the cast iron vs cast
aluminum will be hard to pinpoint. I haven't seen identical saws with
the wheels being the only difference. Usually they go along with all
sorts of differences in the hp of the motor, size of the table, quality
of the tension screw, etc.

I started off as a hobbiest with a G0555. It worked fine even for
resaw. I would think if you are resawing rarely it will suffice for you
as well. I have now moved into a more commercial application, and am
attempting to use bookmatched elements in virtually every piece I
design. This means alot of resawing, mostly of 8/4 african and domestic
hardwoods. I found that with the G0555 I was unable to get cuts that
didn't wander. Meaning when I went to joint the now split book-matched
panels I would loose alot of material, and the bookmatched grain. This
was unaceptable for my application, so I chose to buy a new machine. I
ended up buying a 17" General bandsaw, 2hp dual voltage motor, welded
frame and a huge cast iron table. The wheels are also cast iron. The
difference is night and day. With the general I can easily run 3/4"
blades to the proper tension, something I was unable to feel
comfortable with on the G0555. The extra power, and greater stability
make resawing MUCH faster, and the cuts are wavering much less than
with the G0555.
All of that said, I don't regret the G0555 a bit. I purchased it at a
point that I was working with smaller woods, and less frequently than I
am now. When it came time to sell it I made 3/4 of the money I invested
into the machine back. It's well liked and a solid green machine.
Hope these thoughts help somewhat.

Andrew