According to Beretta USA, the PX4c is a 1/4" shorter and 4oz lighter than the 92c.
My PX4c is
1.1" wide at the frame and slide.
1.2" wide Holosun 407c/507c.
1.2" wide at the old "Fugly/stealth" decocker levers levers.
1.3" wide at the low profile slide catch lever.
Beretta USA says the PX4 Compact Carry is 1.4" wide and the LTT 92 Elite Compact is 1.5" wide. (I don't know where they're measuring)
I have a PX4c with a Holosun 407c on it. It's a great little carry gun. A PX4c w/ a Holosun 507k would likely be even better, but I don't know if LTT does a 507k plate yet).
There are currently no BUIS for the PX4 line. Last I heard, Ameriglo has them on the to-do list, but COVID, etc. To quote Tom Jones regarding The Gadget: "#Soon."
Comparing my RDO Solution PX4c to the RDO 92 videos, the 92 mounting solution
appears more robust than the PX4 RDO solution. All else being equal, if Aaron Cowan level durability is a consideration, my impression is the 92 gets the nod in this particular criteria.
Hope this helps.