No, if you're talking about structural performance. Yes, if you mean looks. The two basic log
shapes are round and square.
Round logs resemble the tree they're cut from. If they're prepared by hand, a logsmith runs a drawknife along the surface and removes the bark, leaving rough contour of the tree trunk.
Logs that are milled round are uniform but not always perfectly round. Some round logs have tongues and grooves or flat surfaces milled on their tops and bottoms for a tigheter fit. Once stacked in place for the walls, however, these logs’ visible surfaces are fully round.
Square logs have flat surfaces. They can also be milled or handcrafted. For handcrafted square logs, a logcrafter hews a tree trunk with an adze, a broad ax or a combination of these hand tools. Milling square logs requires a different set of knives on the sawmill from those used for round logs.
A popular milled log combines round and square. It’s called the D-log. It’s cut round on the exterior visible surface and flat on the interior to resemble the letter D in profile. People like this shape because the flat interior has a more finished look.
Most people favor the look of one shape over another, although neither has any structural advantage. When you’re starting out to learn about logs, unless you already have a preference, you’re better off keeping an open mind about the matter.