From my perspective the BT99 is still plenty capable of getting the job done. As far as I can tell the targets haven't changed and the yardages are still the same.
The BT99 , 725 or the KX6 whichever one you want will break the clays if you do your part
Most trapshooters would be better of buying a BT99, a grand worth of shells, and a grand worth of less than spending $3500 on a gun... MANY more would be better off buying a BT99, 2 grand worth of shells, and 2 grand worth of less than spending $5500 on a gun.
That being said, if you are looking to upgrade, it would make ZERO sense to buy a prettier version of the gun you already own instead of making a SERIOUS upgrade in the quality and longevity when the price is the same.
Rib has nothing to do with it, shoot whatever rib you're comfortable with.
I kinda view your question as "should I put a loud muffler, new paint job, and spoiler on a Honda Civic, or buy a stock BMW, the price is the same".
Im from the old school! I find it beats a lot of new school pretty regular. I prefer proven over trendy. They said, I'd rather put my money into feel. functionality, fit and longevity than fancy engraving. But that's prolly cause Im cheap
If you are searching for a reason to replace the BT-99, then find a high condition Ljutic Mono with suitable dimensions for you and the rib of your choice. The down side is that you will never have an excuse to search for a different SBT. The money you save in a life time of buying different shotguns that are unnecessary will buy lots of targets and ammo. Your scores will thank you. Good luck.
A friend I shoot with has a modified BT with a 3/4" Add a Rib and a PFS and he smokes targets with it. My suggestion would be to do the same to your "old" BT, $1,200.00 and you've got a totally up to date gun. The high rib allows you to shoot a more head up stance and the PFS adjusts all the other BT fit problems. I shoot a KX6 special and absolutely love it but let's see, $6000.00 for a new one VS. $1,200 for the mods to the BT that will shoot extremely well. If you're a long yardage handicap shooter maybe the K would be best but for 16 - 20 yard shooters a modified BT is tough to beat.
I shoot in a trap league with an older gentleman on my team. He shoots a BT99. Somebody recently asked him when he got the gun and he said he bought it when he started shooting trap in 1971. He shoots just fine with it. I don't really think it's a question of old school vs. new. Just a question of what gun fits you and what you can afford.
I own several BT's from the 70's which I shot. 3 years ago I bought a used BT Golden Clays for less than half of MSRP.
It has taken me from the 21 to the 26.5 and from C to A or AA depending on the weekend. My thought process was they are wallet friendly and easy to work on. I looked at much more expensive guns, but I would rather spend the extra cash on shells...and I have.
There is nothing wrong with a BT, it is just the generation that grew up shooting them have either passed, or retired and bought a prettier gun because they could. There fathers shot Model 12's and called BT's a new fad.