Sportives are faster and have a competative edge. Finishing times and placings are published. Route usually signposted. Food on Sportives are gels/bananas grabbed from a table at the roadside and eaten whilst on the move. Lots of blingy racing bikes with no mudguards and a seat pack containing an innertube and not much else. Most sportives are around or below 100 miles in length.
Audaxes are not races. They have a maximum average speed to prevent racing (the intermediate controls en route should not allow you to go through them early). It's all about the distance and finishing within the time limit. Finishing times and/or placings are not published. Food stops are cafes, petrol stations or a car in a lay-by. I've stopped for more than an hour for lunch on an Audax. Route not signposted, you get a routesheet instead. All riders carry 60% of a spare bike in a Carradice Nelson Longflap including three spare inner tubes, a spare folding tyre and some spare chainrings (just in case). Lots of beards, SPD sandals and Brooks saddles.
Audaxes are generally 200km in length and higher although shorter Audaxes (50km, 100km, 150km) are run to get people to try them out.
In other words (and I can't remember who said this first):-
Sportive: Pretending you're racing.
Audax: Pretending you're not.
