For those size limbs, even a 12" Ontario Cutlass would do, once sharp. If you're talking about needing reach from the ground, then of course you'll need something longer. The Ontario is 1/8" thick, and the weight forward design makes it a great chopper. 42Blades does an upgraded version, convexed edge, reshaped handles, and a sheath, it's the best value/price/deal you'll find for one. I think the Ontario 1095 holds the edge better than Imacasa/Condor's 1075. The heavy duty Ontario's can be convexed in a way that they will take less damage, in my experience.
The 18" Ontario @ 1/8" is a bit heavy, it's a good machete, but maybe overkill. Ontario does offer an economy line, it's thinner stock 1095.
The ESEE Lite machete's handle is a bit large, IMO, but made well,
Condors are very sharp out of the box.
Fiddleback's have excellent handles, and sharp edges.
It's the Tramontinas and Ontario's that have no edge to them, and that's an issue for some. I don't have a belt sander, so I've modified two Ontario's by hand, files and sand paper. It's a good lesson to do so, but in the future I want a faster method.