Over the years I have purchased baluns but they are actually not difficult to build. So, I'm planning to learn as much as I can about balun theory and design, and construct some of my own. Some of the baluns I have purchased in the past include high-power capable models sold by DX Engineering, a triple ratio switching balun with 1:1, 4:1, and 9:1 options, sold by Buddipole, and others by MFJ, etc.
I recently built a small kit from Elecraft, the BL2, which provides a medium power capable switching balun with 1:1 and 4:1 options. An interesting comparison was to put it in line with a dipole and record resistance and impedance values, and SWR, as compared with other baluns. I used a RigExpert AA-170 antenna analyzer for this purpose. Although the values recorded were not identical, they were similar enough to make me comfortable that this balun will be acceptable for use. My plan is to use it as part of a portable multi-band linked dipole, and I think having the two different options will be convenient.