I bought a radiator guard years back. It is still new, unused in its box. The reason is that I saw a friend's radiator which was a right mess. The guard had stopped some muck off UK roads being splattered all over the place, but that which got through the grill lay on the radiator hidden from view, eating away at the alloy. Never seen, never washed. I'd rather be able to see it and clean it up.
I did by a radiator for my A9 a good few years ago. I hit an interesting piece of info. Part way through the life of the A9, the radiator was changed. It isn't listed on the A9 fiches, but David Silver have access to more info based on the model VIN. The newer radiator was £100 cheaper at the time and had a different part number. Mine required the newer part number.
But I was curious. I checked all of the components that fit onto the radiator - includint hat part of the frame. All of the tubes, all of the electrical connectors, fans etc. The only part that was different between the A9 and earlier models was the radiator cap !! So I reckon the filler cap of the radiator is different, and that's all.
The models changed considerably between A6 and A8/A9, and I didn't check to see if the A6 and earlier radiator was the same one that was used on the A8 and the earlier A9.
But it is worth looking into maybe. If the price difference remains as much as that.
A broken fin isn't an issue. If the tube to which it is attached is broken, then that is a problem. You'll see the steam if it is broken, or it will be wet after a cooling down after a dry ride.