if its going to be a bedside table gun only.. thats a very good price.. a used G19 is likely going to set you back $100 more than that (or more depending on condition, generation, etc..).. (the beretta is a full 25% cheaper)...
something to consider though...
if you intend on purchasing a quality holster, mag pouch, night sights, and/or any accessories (light, additional mags, etc..).. your total investment in a new pistol is probably going to end up being somewhere in closer to the $650-$800 range (depending on what you want, what items you get, etc..).. that $100-$150 you save on the pistol isnt really all that much when you consider the "all in" cost (could be as little as 10-15%)..
and we're not even starting to factor in the cost of range time, ammo, training, etc.. (for some people less than $100 a year.. but for others can be in the thousands)...
I guess where I am going with this.. is dont let a couple of hundred bucks be the deciding factor.. if you really want/like the beretta... cool.. get it...
but if you REALLY would prefer an M&P.. save a little while longer... and then make the purchase..
an M&P will last you a lifetime.. and the cost associated with the pistol alone is only a fraction of the overall money you are going to spend over that lifetime when it comes to shooting/carrying/practicing/training with it..