I have meprolight on my sp101 and like it. I recently put a big dot(the biggest one) on my g26 and like it very much for a close range weapon. I would not mind the big dot on my sp but not going to spend the cash now.
I have the Standard Dot on my SP101. I had the Big Dot on it. Up close no doubt the Big Dot might be better but for me it covered up too much target to see what I was doing further out. To me the Standard Dot is still very prominent when doing quick aiming.