Neither of the above. It is quite possible to start a roaring fire without resorting to either a saw or an ax, at least in environments with reasonable woody growth.

Tinder is the finest and driest wood material available - I prefer shredded juniper bark, pine needles, or pine pitch. Gather small twigs, various sizes so that you have a fuel ladder - a "teepee" formation is probably the simplest.

Gather dead wood of the right size per Denis's very fine graphic. these will be f various sizes. Break them to the appropriate length by (1) propping them against something solid and stomping them or (2) bashing them with a heavy rock (a wonderful primordial experience!)

If you must carry a cutting implement, I would recommend a Sven saw or a solid hatchet like an Estwing model. In a good many jurisdictions, wood fires are obsolete and potentially hazardous. For the same weight, you can pack a small camp stove and fuel which will cook your food faster, with less danger, but also without the undeniable ambiance engendered by a wood fire.

Today I was just shown a fairly incredible amount of damage inflicted by some axe wielding goon on some very nice oaks in one of our local campgrounds. Please engage brain and think before chopping....