This here is my first 3" build, seasoned with a stretched-X Armattan XLR-3 frame. I finally decided to build it after slowly getting the rest of the parts. The Sirin FPV FC was chosen because of its simplicity and features, as well as the fact that I got a good deal on it. A friend of mine has this frame with a Betaflight FC, which I would recommend (complimented with some EMAX 15a bullet ESC), because doing a 2-stack (4-in-1 plus the FC AIO) was a little too snug a fit if screwed upwards.
Overall I am totally happy with this clean build, and I intend on building at least another 3" in the future, and aiming for a sub-250g build. I am also very curious if I could build a fancy 3" that can fly with a decent action cam, for I would take it everywhere with me.