Using a moving average with a box filter halves the work an attacker needs to perform in an isolation attack to get the chain down to a level where they can simulate the running network.  It also requires you to move the clamping functions much closer in to keep them equally effective, which means they become easy to hit and it's not really easy to reason about the incentive implications of a non-linear difficulty adjustment (e.g. you potentially make it more profitable to mine in bursts).

This has been discussed many many many times before.

When you do not use the search function you risk having an uninformed discussion because the more expert people have gotten tired of rehashing the same subjects over and over again for years.