I've heated with wood now for most of 3 decades. So I have a bit of experience with cutting/splitting wood. Most of my firewood is oak or elm, with some maple/walnut/poplar/cottonwood/basswood thrown in.
And I have several of the regular 6 and 8 pound splitting mauls from the local farm stores. They work OK, depending upon how you use them.
Gransfor makes good axes/mauls. But you also pay a lot for the name, when similar tools will do just as well for the average person.
But the best splitting maul I have ever found is something called a Monster Maul. (Yeah, they trade-marked the name, but other companies make similar ones.) It is a simple BIG triangular wedge welded onto a steel pipe handle - with a foam cushion grip on the end. It weights around 15 POUNDS! The head is an equilateral triangle 6 1/2 by 6 1/2 by 3 3/4 inches, and is 3 inches tall. With handle is stands around 2 feet 7 inches tall. Yeah "piece of pie" shaped, probably around a 30 degree angle on the "wedge" part. That's a steep angle for a splitting wedge. It is amazing what you can split with this thing - even the tough/twisty stuff like elm.
(They do now make a 12 pound version, as well as a 5 pound "kindling" splitter.)
Their literature says to just "let it fall" when splitting wood. That the "weight" of the head will do the splitting. Well, on 1 foot diameter straight grained oak it will, or similar wood. Most of my wood tends to be 2 foot or more in diameter. So I SWING it down! And some pieces can take a half dozen blows before starting to split - especially those with knots. Their literature also says that you can't get it stuck in wood. But I have. And occasionally stuck enough that I had to get another maul to hammer it out.
But that Monster Maul just works so much better than any regular splitting maul that I have ever tried. When cutting wood, I always have it along. I usually pop those 3 and 4 foot diameter oak blocks apart into at least quarters - so that I can pick them up and throw them in the back of the pickup truck. When I'm cutting firewood, I cut and haul it home. The real firewood splitting takes place later. My main purpose is to get it cut and hauled home.
I don't really remember what I paid for it. I think it was around $30 usd. They are usually listed in magazines like Mother Earth News, Farming Uncle, Small Farmers Journal, Organic Farming, etc. A web search should give you some leads
Yes, swinging that Monster Maul around for a few hours will sure make you sleep at night! I've tuckered out several friends trying to keep up with me splitting firewood. (I actually have two of them.) But I also have a hydraulic log splitter for the main work. I go through between 5 and 6 cords of wood a year for heat. (poor insulation in an old 100 year old farm house where the wind rattles the windows on the other side going out!)
Just my humble thoughts to share. Take them as such.
Mikey - that grumpy ol' German blacksmith out in the Hinterlands