For a long time,I subscribed to the 4" maximum philosophy. "A true woodsman needs no more knife than the width of his palm" And I got by for a long time that way.
I lost my field knife one camping trip. At the time, money was very tight and I bought an 8" Old Hickory Slicer. I cut it down to a 5.5" drop point. Re ground and thinned out the bevel and sharpened 'er up.
Tasks that include cutting feed bags,feather sticks, making campfire supper, cleaning the birdsmouth when building rafters and dressing our hogs to be butchered.
I found that having a blade over 5" is almost like having two blades in one. A section near the handle for power or fine cuts and a section nearer the tip for slicing and scraping. I utilize scraping fairly often for removing bark and finishing tool handles and a bit larger blade gives me something to hold onto. A blade a little longer shines in food prep. The Old Hickory has a great hand filling handle that fits me well. A roughly octagonal shape is comfortable as I index the blade for various tasks.A longer than most handle is nice when the hands are tired and cramped or in gloves.
Moras are great. I have one by my side right now and used it all evening. The scandi grind carves nicely. But a couple weeks in the field doing the tasks I mentioned and more, give me a knife just a little longer.
For summer fire prep in my area, i just break the wood leveraged between a couple trees. Anything too large for this gets fed in as it burns as in a star type fire. Faster and safer than chopping or sawing.. Winter brings a boys size axe at minimum usually paired with a Swede saw, though the axe is king for its versatility of chopping, trail blazing, chopping ice, hammering, etc.
Turned into a bit of a long post! haha
NOT MY PHOTO. Very similar blade however. Just picture it with the stock handle.