I'll restate two things that I've noted before: first, that capitalism and socialism spring from the same roots, and second, that I noted early in the discussion that I didn't think the opening question was actually valid - as it is expressed as alternative choices. In short, it's a stupid question.
Briefly, both capitalism and socialism were variations on the theme of spreading "the wealth" among participants. Capitalism was based upon "shares" that represented contributions by "investors", whereas socialism was premised upon roughly equal shares (later, based upon needs) of all "contributors." It was only later with the marketing/trading of shares as investments themselves in "exchanges" that capitalism took on the tenor that marks it out today. Similarly, the broadening application of socialism to larger and larger organizations, then nations and beyond, changed its nature. Both, in essence, though, are premised upon spreading, rather than concentrating, "capital".
In modern parlance, though, both are now focused on to whom power is accumulated. There, I think, is where the error in both lies. Power corrupts, and absolute power corrupts absolutely.