Before you jump on the Big Dot wagon, you can get "Standard" sized dots which are roughly 2.0mm compared to the Big Dot +/- 2.5-3mm dot size. Much more accurate, at speed, and using a Warren Tactical rear (plain black) is better still IMHO. For reference, I started using the XS sights back when Ashley Emerson started the company, around '96-97 IIRC.
I use XS big dots on my xd sc 40. Accuracy suffers some, but at 10 yds it is plenty accurate. Very easy to see in the dark. They are great for ccw, but not a good choice for target guns.
Not IMO. If you really need the crutch of a big dot up close, I guess you could opt for them. Most shooters don't need it and you're really limiting the effective operational envelope of your handgun. Your accuracy at any distance over 10-15 yards will really suffer.
I realize that most engagements will be 7 yards or less (likely 7 feet or less), but I like to be prepared for the unexpected.