Circular sawmill and bandsaw mill are two common types of sawmills that are used to cut logs into your preferred dimensional lumber. It was in the 1800s when (circular) sawmills were first used featuring very large blades. After some time, bandsaw mills were invented. Both are still in use today.
The two major differences between a bandsaw mill and a circular mill can be understood in terms of production and kerf.
Kerf refers to the width of the cut or notch made by the blade and depends on the thickness of the blade. The blade on a bandsaw mill has a thinner kerf (3/32 inch, or 2.5mm ) and produces far less sawdust than a circular sawmill, which has a 1/4 inch (or 6.25mm) kerf. The thinner the kerf, the more lumber is produced from each log, making the bandsaw mill with a narrower kerf the more efficient saw.
You'll also want to consider also the waste each type of saw creates when cutting logs. Bandsaw mills produce far less sawdust than circular sawmills since they have thinner blades.
In terms of accuracy, however, circular sawmills produces lumber which require less planing than bandsaw mills.