Bandsaw blade width
While it is not what you might expect with wood bandsaw blades, but it is true that the narrower blade can produce a straighter cut than a wider one. This is because the force of cutting the material can make a wider blade deflect sideways. This is not the case with a narrower blade which tends to veer backwards, rather than sideways. However, when cutting thicker material, a wider blade does not wander that much as the back end helps drive the front of the blade.
When cutting a curve line, wood bandsaw blades with narrow widths are able to cut a smaller radius than a wider width. When sawing hardwoods and high-density softwoods, it is advisable to use as wide a blade as possible while a low-density wood can use a narrower blade.
Bandsaw blade thickness
Blade thickness is typically expressed in terms of actual measurement but it can also be reported in gauge. When it comes to thickness, the general rule is that the thicker the blade, the more tension there is, which means the straighter the cuts. When cutting or sawing hard knots and dense woods, it is recommended to use wider and thicker blades because of their extra strength and to prevent breakage. They also deviate less when resawing.
However, thicker wood band saw blades are hard to bend around the band wheels and they generate more sawdust. The rule of thumb, in this case, is that smaller diameter band wheels require the use of thinner blades to avoid too much difficulty when sawing.