I have experience with the 3 main Mossberg pump shotgun platforms. My opinion of the 590A1 is that it is an overbuilt pump shotgun that kicks behind and will work as hard as you care to work it. I kind of prefer the 500 for general use because it's not as heavy, I also like the Maverick 88 but I really prefer the controls of the 500 and 590.
When comparing the 590 or 500 to other models such as the 870 or the Winchester, I tend to favor the Mossberg. Do they all work? Absolutely yes. But I LIKE the way the Mossberg's work more than the rest. I've also experienced greater reliability with the Mossberg's, not much at all, but enough that I remember, even if it can be chalked up to user error. As far as disassembly goes for maintenance, once you've done it a few times it's not bad at all, although I must say, the Winchester is about the easiest I've run into. If you want a 590A1, I will tell you to go ahead. With it's reliability, ruggedness, intuitive controls, and general ease of operation, I don't think it gets much better than a 590A1 for a fighting shotgun. As for the variety of 590A1 models, take your pick
Also, whatever you end up with, practice with it! Loading, shooting, Safety... get to know your shotgun very well, and enjoy it!