No personal experience with sx4. I have an sxp, I like it.
I do have a m3500. I like it as well. It's been dunked and covered in mud while duck hunting and has always gone bang. It handles any duck load fine. It doesn't cycle light dove loads too good at 0* angle or less. From my research it needs a good break in with heavy stout loads to loosen up the springs a little. I've added a larger safety and bolt lever. I also have a mag tube and clamp I put on it during the off season. I don't think could really go wrong with either. But my vote would probably be the stoeger. I was gonna say get the one the matches camo you use but since doesn't matter.
