Marketing dept's ...for gun mfg's...name guns all kinds of different ways...and its really confusing to new shooters ( and it doesn't really mean anything !! ) in terms of how you use the gun.
Its hard to keep up with Browning Citori models over the years...in their current catalog alone ..there are 29 models in the general Citori line of O/U's...in the 725 series of Citori O/U's there are 23 more models ...and in the Cynergy line of O/U's there are 9 more..../ and they're all a little different in some way...
All of the Citori line share one thing...the barrel to receiver connection - and its incredibly strong..and probably the single biggest reason most any Citori will be a 250,000 - 500,000 shell gun...or more. It can be abused by owners that don't grease it properly and are careless when they assemble their guns...by gouging, scratching, etc...( so look over the barrel to receiver connection for wear or gouges ).
Stock dimensions are critical ..to figure out what "Fits" you ...so it hits where you look / because there is no rear sight on a shotgun, so its critical it hit where you look / and so it doesn't beat the stuffing out of you. Too short a length of pull, too long a length of pull, too much drop at comb, too much drop at heel - or not enough drop --- or too light, or too heavy ...are all things you need to figure out.
I love Browning O/U Citori's ...and I have 5 of them, that are my primary guns....but 80% or more of the Citori's will not fit me personally. I need a parallel comb gun ..where the comb is not angled, its parallel to the rib - and I like an O/U with 30" barrels ..and gross weight at about 8.5 lbs...( and it doesn't matter if its a 12ga, 20ga, 28ga or .410 ...)....
Too much drop at comb, for me, means the stock pushes the meat in my face up against my cheek bone as gun recoils...and it beats the stuffing out of me / and at 6'5" and 290 lbs that is not easy to do...but a gun that doesn't fit ( like most of the Lightning series of Citori O/U's ..will bring tears to my eyes after about 20 shells....when a gun that fits me, I can easily shoot 300 shells a day with no soreness.
My go to gun....for Skeet, Sporting Clays, 5 Stand, and live upland birds...is an older model called a Citori XS Skeet ...in 30". My go to Trap gun...is the Citori XT Trap model..with 32" barrels and around 10 lbs... For Trap, I want a gun, that is heavier, so it swings more smoothly at Trap where the birds do not give you as much left to right movement...and so its point of impact is a little higher ( like 70%/30% over the point of impact, because Trap is a game we shoot ideally when the targets are rising...not falling or sliding sideways...
So for Skeet, sporting clays, etc.../ I want a gun that is heavy enough to be smooth ...but still nimble enough to handle hard crossing targets one way and then the other, or dropping targets, or rabbits, etc...
I could shoot my Trap guns...for Skeet, Sporting, etc....but they would feel heavy and clumsy.
But it comes down to what you like...
Upper body strength, length of your arms, the dimension from your shoulder to your cheek..are all factors. One of my adult kids...can shoot a Citori 625 sporting series gun very well...it fits him / it beat the heck out of me. Another adult kid...can shoot the Lightning series very well...but he can't shoot the 625 series..../ but they can all shoot the parallel comb guns very well....