At the present time there are about zero options for the ARX, anything would have to come from Beretta other than an optic.
The AR? Oh, gee, let us count the ways,. Better yet, define what range and target you want to shoot at, which then get into which cartridge, of a half dozen that are popular right now, and barrels at 7", 10.5", 14.5", 16", 18', 20", 22", and 24." And there are a lot more in between. Add three or four profile weights from pencil to bull.
All of that custom tailored to doing the optimal job on that specific combination of range and target. It sets the cartridge, barrel, gas length, optic, handguard, mag capacity, then in declining order, grip and stock.
You could wind up with a 10.5' pistol, a 16" carbine, or a 20" Designated Marksman build - for the singular purpose of deer hunting. One would likely fit your local circumstances better than another.
If it's a decision based on "I just want one" then buy a decent quality one and find out how it works for you. Then, you can change it, if you want. The Beretta, not so much, it will be an ARX for a long time, a proprietary design no one can copy is usually trapped in one configuration.The SCAR has been out for years and olly lately have some items become available from the aftermarket. The AR from the beginning had 20" and 10" barrels side by side in Vietnam, which set a lot of precedence for the market to follow.
Follow your hearts desire, but the number cruncher side of the brain will remind you that for the price of the Beretta, you could build two different AR's in todays market and enjoy both. But - they won't be Berettas, either. And having bought an HK in early 70's, nothing else will do. It was fine - as is - for a long time. Until I realized I could build AR's and get exactly what I wanted.
So, now I'm finishing the pistol build and it's going to be an interesting fall.