I agree with 42B, the thinner the better for me,
For me a knife is primarily a cutting tool, food prep, opening packets, dressing game and carving are the main tasks required for my a belt knife on most trips, for me I find 1/8 is perfect for a knife with a blade length around 4inches, I have never had any problems battoning with knives of this thickness and never wished for anytrhing thicker.
I think with knives now makers and manufacturers are over building knives as people tend to use knives for wood prep etc instead of there primary function of just cutting, for me I would rather have a tool dedicated to a specific task and excell at that one task rather than being a jack of all trades doing tasks to a lesser standard, for example a hatchet/axe and a folding saw is unbeatable for wood prep in heavily wooded areas in colder climates and I would much prefer this than a 1/4 inch thick prybar that will do the job and slice a sandwitch but do it with less finesse, a thin 1/8 thick knife for gutting an animal will work wonders where a thick knife will do the job and split firewood but to a far lesser standard.
this is all just my opinion based on my years spent in the bush, everyone is different and I dont think thicker or thinner blades are better or worse it comes down to what the individual prefers, what works for me might be a complete pain in the arse for the next guy, so what Im trying to say is a combination of tools specifically designed for a set purpose is what I prefer and this always includes a thin belt knife, this does change tho if I only want to take one tool that must do all bushcraft tasks something a bit thicker for added peace of mind is good to