Dan,

I will ditto the comments about Prazi lacking precision. The base is very small and easily wobbles. They are handy for rough shaping, and I use one to cut sweeps and radiuses, then finish with hand tools. I am fabricating a larger base to improve accuracy. A sharp (!) chain is very important.

Another thing is that the frass piles up on top of the wood, obscuring the marks and lines. I added a compressed-air jet to mine that blows the dust away.

For scarfs, I think a Prazi would be no advantage. I cut mine very much the way you do, and achieve almost invisible joints. I use a 5 point ripsaw with a lot of set; finish with chisels.

The specific design and dimensions of any joint can be selected to suit the capacity of the particular tools on hand, with an eye to making them efficient to cut. There are dozens of possible styles of scarf.

Except for a very few circumstances, a chainsaw (gas or electric) can do anything the prazi will, with careful technique.

Good luck.

Pete