Through hole I've moved away from C shape to using D shape, they are versatile. A rule of thumb is measure the size of the pads you're soldering the most and aim for only slightly larger than the pad and use good temp control.
D24 and D32 are useful. It is sometimes easier (as long as your not going crazy) to just bump up the temp on large thermal masses and then knock it down when you are done. S3 will brute force anything.
For SMD it depends on your purpose and size, I have S4, D8 for precision and C2, C3, C4 for jobs of all sizes.