I had the Big Dot front, and while it was great for up close (as that is what it's designed for), I opted to change it out for a standard dot front since I use the same gun for the range as well.
There is always a trade off with anything. With the Big Dot front, you gain speed picking the front sight up (super easy) while that same sight obscures the target at ranges greater than 15 yards. Even with using the top of the sight like they say, the fact is that it is still difficult to get a nice grouping at that distance.
After installing the standard dot set, they seem more like what I wanted. I usually go to the range once a week, and the new sights were waiting for me when I got home, so I'll have to wait until next week for a range report on them.
is a good discussion on the differences between the two.