I was trying to decide this as well. I ended up buying the Mossberg 500 Home Defense / Field Combo from Cabellas. It comes with a heavy-walled 18.5" "Breacher barrel" with a white-dot sight and a ribbed 28" field barrel with three different chokes and dual bead sights.
Picture: (I added a LaserLyte tri-rail and a NC Star weapon light)
Only thing I did not like was the stock/forend. The stock was a bit to thin where your hand grips it for me personally. Also, the forend was the cheaper "pinned" style you find on the Maverick 88's. So, I bought a Hogue overmolded stock/forend set ($40) and a Promag PM194 7 5/8" Action Slide Tube Assembly ($40) and I like it much better now.
Picture after the modifications: (you can see the grip area is a bit fatter and curved, which I found more comfortable for me.)
All told, it was still cheaper then a 590A1 and I have the extra sporting barrel for trap/skeet .... it had everything I was looking for.
Just thought I would share.