Basically the easiest way to select what type of lopper to use (same principle for secateurs) is that you use bypass for softwoods, anvil type for hardwoods.
Ratchets loppers are good, especially if you don't have upper or hand strength.
Fiskers patented geared loppers are good too, but do have a slight weakness in that they wear and twist where the pivot bolt/blade is when they are used incorrectly. But no different with any other lopper when incorrectly used, but the twisting is an additional fail point.
I do like the rolling handles on secateurs, which I have my late MIL's Fiskers style, but only good on really soft stuff, as you cannot put too much strain on them, as I have a few slipped cogs at times. I use ARS VZ8 personally, due the simple locking/unlocking mechanism and the chrome blades. Telfon coated blades are a scam, as you don't cook with them.
Most well respected brands such as ARS, Bahco, Barnell, Cyclone (the older stuff before being made in China), Felco, Fiskars, LOWE (if you can find them) and Wolf, are all about the same in quality. It just depends on what you need, whether narrow heads, or larger gated openings or length of reach, chrome plated etc.
As Fred mentioned, the longer the handle, the less strength you need to use them. But you need to have the space available for the arc of the movement for the handles.