No to SPD's as my knees don't like them.
Yes to Crank Bros.
No to flats unless I am planning on perfecting my monos or tricks (which is never!)

…over 10 years of running spd's but recently moved to flats with studs with 510 shoes….well impressed! …would still use spd's for long distance xc and road but finding flats great for sub 20 mile lake district rides….