The thermal mass or R-value issue aside for a moment.
I think the first decision to make is: Do I want to see a lot of logs stacked on top of each other and live in a wooden "box" ( walls, ceiling, floor furniture) or do I prefer less wood and admire the joinery? Sure wood is a beautiful/interesting material to look at but if there is too much of it at once it will be overwhelming.
Are you thinking high or low maintenance house?
Logs should be sealed to last longer. American TFs are enclosed and therefore protected from the elements thus last longer. A log house can "show off" because of the way it is build in and outside. An American TF cannot unless you get to see the inside of the house.
Thermal mass is a great thing and so is a good R-value and an air tight house. Then there is sound control. I would assume that SIPS, though they might be a good insulator, are not necessarily a great sound deadener. Where insulated concrete certainly is. So, lots of choices and decisions to make here.