Please tell me about chokes, specifically why one brand is better than another. I understand what a choke does, but why is a Carlson flush mounted full choke $8.30, Browning full $28.99, Trulock $38.49, Briley Full $39.95, and Briley Spectrum Mach 1 $64.95? (I'm looking at prices on MidwayUSA.)

Also, what is the benefit of an extended choke tube versus a flush fit?

Shotgun in question is a Winchester Super X2 (SX2) with factory threads for Invector Plus chokes.

I already have a modified choke which I'll probably run most of the time anyway. I thought about getting a full choke as well as a skeet or IC tube. The gun is used for 3-gun competition only.

Extended choke tubes are usually easier to change, if you are into hunting birds.. Most (ex) tubes have what they are (IC,M, F) on the extended part.. they also provide muzzle protection. Depending upon the tube itself, or so ive heard, and ive got a full set for my citori, is the extra half inch or so gives a little bit longer range.. Im not sure about that, as ive noticed no real difference aside from the shot pattern itself.  The best way to figure out which tubes you like is to buy the cheapies, pattern them for the loads you will be shooting, 10,25,40 yards and then if you want to step up to more expensive tubes go for it... buy stay consistent with the loads or the patterns will change and you will have no idea which tubes work for what loads.. just my 2 cents as Sept is fast approaching.. fly fly little doves....

I've never noticed any major advantage with the top o' the line Briley chokes vs. cheap OEM choke tubes (at least in Rem-Chokes).

I'd just buy the cheapest extended chokes you can find. They are much easier to change & easier to make sure they are on tight after shooting a round of skeet/trap/3-gun.

Did you get your CDNN catalog?
Pages of chokes for sale.

I didn't think to check there.  Thanks!

Go over to some shotgun website and ask there.

It would be like one of them asking 'what is the difference between this Leapers scope mount and this LaRue one' here.

Quality of machining, materials, concentricity, etc etc.

While the average joe may never see the difference, the competitive shooters will.  Kinda like our Tier 1 guys here.