Better than "best" would be completely separate implementations with separate code bases, preferably in separate programming languages. Separate teams evolving a common code base continues the risks of monoculture.
I think it's not needed to invent everything new since already thousands of thousands of work hours flew into the code. It would be sufficient to review code to be implemented, change code who is not working properly and so. Then all bitcoiners would have a way to chose the implementation they feel is the best at the moment.
Though this will die quickly since one of the first decisions will be 1mb block or 2mb block, which will mean 2 different blockstreams and the same bitcoins on different addresses in each blockchain.