In reality the ideas overlap. What is clear is that the utopian extreme of 'from each according to his ability, to each according to his need' cannot work. Because human beings are both altruistic and selfish, both instincts must be accommodated. The problem is therefore not one of choosing between extremes but one of balance. Socialism or communitarianism is a necessary counterweight to the individualism competition engenders.
Crutches are bad but helping hands are necessary.
It does not matter whether we use 'socialism' or 'communitarianism' so long as we are clear what we intend and what the pitfalls are. We should not appear to be changing religions. To be sustainable, our practice of socialism has to conform to the market. This is the way the NTUC works. This is the way Japanese corporations look after their staff.