Hi... for me "someone" is more precise than "somebody" eg : You try to help someone (your friend) or you try to help somebody (among others)

it's hard to distinguish the difference from each other but I think, if for instance you're referring to anyone from a group known to you, "someone" is preferrably used to describe an individual. for me, "someone" is more 'personal' than "somebody" which is more 'general'. don't be confused about these two words anyway. they can be interchangeable in most case - just like "anyone" and "anybody". :)

I agree it's a matter of personal preference.

There is virtually no difference. You would be completely correct in using either one. Some people use “someone” more often when they are talking a group of persons, but don’t know for sure who the one is; “somebody” is used when it is not that important who the person is. This is personal preference, however, and I'm sure nobody would notice very much (if at all) if you used either one.