I like a handle with good retention capability and a lanyard hole on my large knives. It shouldn't have a top guard, and since you note that we can already have a smaller fixed blade, I'd want a good chopper that can make short work of delimbing, battoning, etc. Removeable scales are a plus as is a finger choil.
Assuming they are all the same thickness and steel, I narrow it down to #1, #4, #5, or #6; leaning toward #1 because of it's size. #6 gets the nod for having a choil, which i like, but the handle looks uncomfortable and the blade is not very big. But overall, these 4 look to have decent handle retention, a stong ramp in front your index finger to keep your hand off the blade if the going gets slippery, as well as a ramp behind your hand for retention when chopping. Plus they all have lanyard holes and removable scales.
- #1 looks like a good chopper. The handle should retain well but I would like to see a choil.
- I didn't pick #2 because there is no belly and the handle shape does not look like it would retain well when wet and chopping. The blade would make a great chopper, but if you can't keep it in your hand, what's the point. Plus it would suck for battoning given the shape of the spine.
- #3 has a decent blade shape but the handle looks slick with nothing to keep it in your hand when swinging.
- #4 looks decent, I like the blade shape and would want to add a choil. The handle looks comfortable and should retain fairly well, but not as well as 1, 5, and 6.
- #5 has a cool blade shape and would make a great spear, but that's not what I use my large fixed blades for. Handle retention should be very good and it looks like you could use the pommel as a fairly effective hammer.
- #6 has a useful blade shape and a finger choil, which is nice. The handle should retain very well but looks uncomfortable.
- #7 and #8 look like they would not be good choppers at all. Handle retention looks mediocre, but for a smaller fixed blades they look like they would be good for most smaller tasks.
Overall though, I suppose I would lean towards #1. When you say large fixed blade, I'm thinking something with a lot of capability such as an RTAKII or Junglas. The caveat of already having a smaller fixed blade makes the choice easier for me. I don't need a "Jack of all trades", just something with capability that exceeds the smaller knife in my kit.