Try them all....
I had my mind set on a Ruger 20 Red Label for chasing around my birddogs in grouse country...until I picked one up in a pre-purchase inspection. It felt like a dead stick, so I decided to find something that fit.
I went to a good gun shop (the kind that smells like Hoppe's #9, not health and beauty aids) and had the owner put the Weatherby, the Browning Citori, and others on the counter for me to look at.
After taking my time opening, closing, shouldering, etc, I came away convinced that - for me - the Citori was the gun. It was about $1300, but it has been money well spent.
In other words, go look at as many as you can, take your time, narrow them down one-by-one, handle them, shoulder them, and get the gun that fits. You'll be happy in the long run.
And I think 20 is a fine gauge for Pheasants.