I have an avon on the front .... it is nice and sticky, you can feel it on a hot day.
That gave me weariness about how soft it was. My buddy on a raider on the back tire has an Avon cobra and ate through it in 8000 km. If He can do that on a raider I would probaly kill it much quicker (I ride much more aggressively than he does).
I went with exceedra max on the read and it is lasting well and sticks fine. It does not feel as sticky as the cobra, about the same as the metz, but it is not showing it's wear yet and that's after a good 4000 km so good news there.
The cobras also have a wear warranty, which my buddy with the raider is trying to excercise, will let people know once we have results.
My thoughts .... cobra on the front is a no brainer, I will do that every time. Cobra on the rear is a good choice, exceedra max is good to, comes to preference.