The implication here is, if you run steam locos, many of them have power pickup only on the right wheels, while the left track power pickup is on the tender. When the loco bridges the gap on the right rail with a Digitrax booster, polarity will flip. But, with a Wangrow booster, that will not cause it to flip. And, as soon as the loco is completely on the reverse section, the train will stop because it will not be getting any power at all, with the power pickup of the loco being of the same polarity as the power pickup of the tender. The solution for Wangrow boosters is to add additional power pickups to the loco, in the form of power pickup shoes, or adding them to the wheels.
Boosters also have a way to switch voltages, to varying degrees, for a variety of scales.
The Lenz booster has a jumper for larger scales, but recommends using sets of diodes to reduce voltage from HO scale to power N scale. Digitrax and Wangrow have toggle switches for N, HO, and G scale. But, voltages are different. Digitrax's earlier DB100 booster puts out slightly more voltage. Regardless of how much voltage the booster puts out, you can manipulate it to some extent.