It's not the .20 lines that are the problem rather the lack of +EV opportunities in these .20 lines. For example in hockey, 5Dimes does a .10 line but rarely has the best number on the board since Tony doesn't put numbers out that are different than what Pinnacle does. BetOnline's .20 numbers are great though since they sometimes intentionally inflate one side. Baseball is bet the same way hockey is.
SIA has .15 baseball lines and are significantly better than all the other books who offer .10 lines and move whenever Pinnacle does. Wagerstreet is worth looking into for a small bettor <$300. Bodog dishes out some bad numbers too. BetJamaica is a good baseball book. BetPhoenix if you can get their dime line. I think BetOnline is working on a dimeline. Rebatewager as .10 numbers. Same with Sportbet although they were acquired by 5Dimes and their lines have tightened a bit. Matchbook is solid but you're going to be betting at expected value all the time, more of a tool to use than a place to bet.