Tradesports are decent. They're one of the best for baseball, as they seem to carry more in play games than any other exchange. However, they have the most awkward interface out there, as well as the most uncomfortable comission structure. I'll move some money there for the bases, but nothing grand.
About Betfair vs Matchbook, the question was not about price, but liquidity, I dare say that Betfair has 10x what MB matches, even on a worse price.