American writer/researcher Tom Roster has patterned literally thousands of rounds in empirical testing of chokes & chokes tubes with both lead and steel shot ... as well as having done considerable parallel research on chambers, bores and forcing cones.
Some of the highlights I remember from reading his stuff was that he found no significant advantage, all other factors being equal, to ( 12 gauge ) bores being overbored to more than .740", nor forcing cones longer than 2-1/2". As to chokes, parallel/conical designs performed better than straight conical of the same length, and longer chokes - up to 3" - did not show significant advantage with steel or small lead shot sizes, but did with larger lead shotsizes ( 6's and larger ).
From what I have found myself (using a Baker micrometer bore gauge to verify choke dimensions - not everything is "as marked" - and shooting probably a couple of hundred pattern sheets) that choke for choke, I couldn't determine any meaningful patterning advantage or difference between Beretta's flush-mounted Mobil chokes and their extended Victory chokes, nor their flush-mounted Optima and Optima extended chokes with 2-3/4 dram equiv. size # 7-1/2 lead factory target loads.
I've patterned a few aftermarket extended chokes, including ported and non-ported designs, from Briley, Rino, Seminole, Teague and a few others. I found that the OEM stuff worked just fine ... so resisted most of the aftermarket choke advertising & hype.
I believe some of the extended aftermarket stuff may be advantageous for large lead shot use ... i.e., to coyote and turkey hunters, card shooters, etc., but I just haven't any experiance there, and shoot mostly Kent Impact at waterfowl, so don't have much offer vis-a-vis steel shot.
Have to confess though that for target guns, I do like the convenience of extened colour-coded chokes, and don't mind having to to check or re-tighten them occassionally between stations. The old 870 works just fine with standard flush mount Rem-chokes and for upland field guns, particularly SxS's, appropriate fixed chokes and double triggers work for me.
Just my 2 cents worth....