"what's a better investment and why ? TCredits or S-Builder Co-op?"
My opinion is your best investment in the long run is the S-Builder Co-op, reason being with S-Builder you will be receiving team members whom with a little motivation can become your next team leaders, with T-credits once you spend them,(oh well), granted it may take a little time for S-Builder to kick in but I think it is well worth the wait.Hope this helps you to make a decision.