Actually, most of the top shooters in every clays game shoot o/u's. There are a LOT of auto shooters out there, but by and large, o/u's rule the upper ranks in skeet, trap, sporting clays and FITASC. Todd Bender and Olympic Gold Metal winner Vincent Hancock, both skeet champs shoot o/u's. George Digweed the multi time world champ in sporting and FITASC shoots an o/u. And just about all the other sporting champs shoot o/u's. Brandon Powell, Will Finnell, Bill McGuire, Gibben Miles and the list goes on and on.
The thing is, their guns FIT them. I know what you are talking about when you say they kick .... if you shoot one that does not fit you, it will kick like a mule. And the truth is, the lower priced o/u's are the worst about kicking because they are made to fit the masses. Recoil is directly linked to gun fit. The better the fit, the less felt recoil.
I agree with you in that a good gas gun is a better choice when looking for a good usable shotgun in the $400 to $600 price range.
I myself shoot an auto 90% of the time, it's an old Winchester Super X model 1. I own 2 Browning o/u's and I shoot one of them on sub ga events such as the recent NWTF shoot in Ga. The reason I shoot the auto is that I shoot it well and it works for me..... Sure it would be nice to shoot a super fancey gold inlaid o/u, but the X's on my score card are worth more to me than how nice a gun im holding. And one of my Browning o/u's is super nice with gold inlay.
As I said, I agree about the semi-auto being a good choice, and the Beretta 390 or 391 is tops. A Remington 1100 or 11-87 is also a fine choice.
I started out with an o/u because the skeet club I was shooting at required you to pick up your hulls. Shooting the o/u made it a lot easier to keep track of them without having to pick them up. Also I reloaded and it was nice not having dirt and grass on them from being on the ground.
Sorry to be so long winded, I just have gone through all the scenarios in the past 20 years and hope some of this helps someone else.