I shot my first couple dozen rounds of Sporting Clays with a Winchester '97, 28" tube, full choke. I do not recommend such a rig. I moved on to a Remington 870, 28"/modified, the an 1100. It had a 28"/modified barrel as well, so I bought a 30" Rem Choke barrel for it and my scores went way up. That being said, don't get sucked into an arms race with your fellow shooters, or yourself. It's east to think that you'd break more birds with "X" gun or "Y" barrel length. Get a shotgun that fits you, and go shoot it. I don't draw a line between competition and hunting guns; my best clay guns are also my best hunting guns.
If I was starting over, and money was no issue, I'd have a Beretta 686 or a Citori with 30" barrels, interchangable tubes, and a quality reloader. I'd have the stock fit to me and fitted with a quality recoil pad.