IHMO the only advantage of a separate tack line is to be able to raise the spi faster around the can when sailing duo. Solo, it is faster to have only one line. I don't buy the argument that you can control the tack separately: with the one line setup you just release a little bit of halyard and your spi will balloon more, a little from the top, a little from the bottom, I don't think a couple of centimeter higher or lower is going to pay enough for the complexity of yet another line and yet another cleat.

I use a spinlock on the front beam, not a cam cleat, and I prefer it that way. Some people hate spinlocks, personally I like them for that particular purpose.