The market for bandsaws has settled on a common two wheel design. The diameter of the wheel determines the machine's cutting capacity.
The models differ in size and quality of their frame. Larger, heavier models have stiffer frames. This makes large machines track better and last longer than smaller models.
Resawing vs curve cutting
A resawing bandsaw requires power and bulk to push the blade through a lot of stock at a time. Resawing is best done with a wide blade. A motor with at least 3 HP is recommended.
Curve cutting is much less demanding on the saw. The smaller, more agile blade used for curve cutting takes much smaller bites out of the workpiece. Because of this the bandsaw itself can be much smaller and less powerful than a model made for resawing needs to be.
Bandsaws are limited by their throat size and cutting height. Purchase a model that is large enough to support the work you do most often.
Larger, heavier bandsaws have stiffer frames than smaller ones. In general the blade tracks better on the larger models, especially under heavy load. Small bandsaw perform well when working on smaller stock. For resawing bigger is better.
The smallest models with open stands have limited capabilities. Their components have too much play to reliably make cuts in medium size stock. These models are best used for curve cutting in small stock where perfect accuracy is not required. On small stock small bandsaws can make cuts the larger models are not capable of.
If you plan on using the bandsaw for resawing, purchase model that can mount a 3/4" blade at minimum. Wide blades track better than smaller ones do.