They are almost the same light, one is Xenon and one is LED. If you will ever need IR with it, then you have to get the 8AX. The 8AX has approx 110 lumens and runs for 50 minutes. The L7 has approx 100 lumens and will run for 2.5 hours. Both are rechargeable. The L7 is about an inch longer and about 1.5 oz heavier, all of this is due to the LED assembly.
In my own opinion, I like the output of the L7 better.
Are you planning to holster the light? If so, the L7 requires a nylon holster where the 8AX can use the polymer or nylon holster.
Hope this helps.