30D 'more light sensitive' than 40D

Recently I've seen alot of posts in 30d versus 40D threads listing '30D is more light sensitive than the 40D'.

I decided to do some research into this as I've had a 30D for some time, recently bought a 40D and didn't really understand the comment.

Based on my conclusions, the comment doesn't really make sense and I'm hoping someone can explain to me if a) my calculations are wrong or b) the problem is a theoretical one and isn't actually a problem at all.

From what I understand, Canon basically calibrated the ISO speed of the 30D incorrectly making an ISO of 100 effectively ISO 125.

With the 40D, the 'mistake' is essentially corrected, so ISO 100 = ISO 100.

Now, the scenario is that you are shooting a scene and you have your 30D set to ISO 100 (125) and, let's say, a shutter speed of 1/250 and this gives you a good exposure.

The guy next to you is shooting the same scene with his 40D with an ISO of 100 and sets the shutter speed at 1/200 as the sensor needs more time to produce the exposure.

Checking the histogram viewing screen, the 40D users realises his shot is suffering from handshake, so dials a *slightly* higher ISO, raises the shutter speed to 1/250 and shoots the correct exposure when compared to the guy with the 30D.

Based on the above scenario, I really can't see the benefit of the comment '30D is more light sensitive than the 40D' and I certainly can't see why this would in any way affect your decision to buy one or the other.

Forgive me if I am missing something fundamental here - sometimes when you start to deeply investigate something 'you can't see the wood for the trees'.

Any responses much appreciated.

It's when you're at the extremes that this starts to matter more. If I'm shooting low light sports and only have enough light for f/1.8 @ 1/400 with ISO 3200 on a 30D, I would need to set the 40D to 1/320 to get the same exposure. This could be the difference between a sharp image and one with too much motion blur in it. You could just set the 40D to 1/400 and adjust exposure in post, but then you increase noise--not by much, but you do.

So it's true that when adjusting both the ISO and shutter speed are possible that this sensitivity difference doesn't matter. But when you're up to the max/min on one or the other (or both), that's when it makes a difference. How much? Not really anything to be up in arms about, and certainly not anything to make you buy one over the other.