First, have you gone to shoulder them all yet? I was originally set to buy the SX3 until I went in the store and shouldered one. It did not fit me very well. I have tried the different shims and other SX3 models to make sure it wasn't an one time thing. If it doesn't fit and feel like an extension of your body, then there's no point.
I ended up shouldering both the Maxus and the Versamax. I walked away with the Versamax in the end. I'm really happy with it and it has been a godsend for my back (was in a car accident, messed up my back) while shooting 3" magnum and 3 1/2" shells.
It feeds all the ammo without any FTE or FTF. I found a topic on shotgunworld that attests to the durability and effectiveness of the Remington Versamax. It also touches a bit on the shortcomings (repairs, warranty replacement); however, they are far and few in between.
Having said that, I think I would have a hard time finding a shotgun that can reliably eat and fire a wide range of shells from 2 3/4" target loads to 3 1/2" shells.
Also, I recommend taking a look at the Weatherby SA-08. It was an interesting firearm that fit me really well. I ended up not buying it because I didn't like the idea of changing out the gas pistons based on whether I want to shoot heavy or light loads.