Well quite frankly, I can tell a difference in my tanks. The regular glass just doesn't look as clear as my low iron glass tanks. But the difference is not that noticable.
I guess for me, it would boil down to the additional cost for the low iron glass. I mean if it's twice the cost of regular glass, then forget it. But if it's a 20% bump in price, I'd consider it.
Because barring everything else, the tank is the only item that you can't easily upgrade. Filters, lighting, powerheads, even tank stand are easier to swap out. But trying to move substrate, live rock, corals, fish, invertebrates, etc, etc, etc, would be a royal PITA. No to mention the stress to the livestock, and possible losses.
Thus I'm in the mindset that buy the best tank I can afford (so long as it's not twice the cost). Everything else can be easily swapped out later. Just my $0.02.