PotCoin has the biggest community (9th out of all cryptos according to coingecko) and so I think it is the best. More services and merchants than any other weed coin. The only reason it isn't getting much attention is because there isn't any gimmicks to exchange it for weed causing short-term pumps.

The legality of selling weed for crypto is uncertain and the PotCoin developers are leading the way for making significant changes for all weed coins.

Check it out:
http://www.docdroid.net/ry44/request-for-statement-of-position-virtual-currency-2-5-15.pdf.html
http://www.reddit.com/r/potcoin/comments/2z2rc3/update_on_request_for_position_from_the_colorado/

At the end of the day if any weedcoin is going to succeed, it needs to be 100% legal (not uncertain) that it's legal to exchange weed for crypto. That is when weed businesses will really start adopting it.

I get the feeling a lot of people just vote for what they're bagholding