Rec let for stat/biostat PhD programs. Many options - cannot decide

[bumblebee2408]

I'm applying to PhD program in stat/biostat this fall. I have two rec let from professors I did research with. I'm deciding for the 3nd one from the following possibilities. I'd appreciate if someone can offer advice.

1. I'm doing thesis with a professor whom I plan to ask the 3rd letter from. My concern is that the thesis is a continuation from my summer research with one of the two profs I will get the letters from. So I don't know if it lacks diversity. 

2. A rec let from Real Analysis prof. I'm doing pretty well in class. But I don't plan to apply to programs with Measure Theory though...

3. A rec let from Cs Algorithms class. 

Any recommendations? Thanks!

[bayessays]

If all three are from quantitative professors, get the one that will be the most positive and have the most to say.  I would guess that's probably 1.  If you have some poor math grades, maybe the real analysis prof will help, but if your math grades are good I'd probably go with 1.