I've had the ergo and the ergo sport so can comment on the differences there.

Ergo sport is thinner material, so was excellent in queensland for breathability.

Ergo sport is harder to put on yourself since it has thinner material, the straps don't stay in place as easy and twist as you put it on (and gives me the absolute irrits).

Ergo sport has clips on the end of the hood which are harder to put in place by yourself, whereas the standard ergo has snaps - much easier.

Ergo didn't fit on my DH - he's 6 foot 7, and even with the waist extension it didn't fit. The Ergo sport fits him with the waist extension.

Other than that.. they're the same! haha

I'm looking to swap my ergo sport with a normal ergo, just because the other one irritates me so much that I don't use it. And its such a good carrier that I hate it just sitting there.