I split everything by hand. If a maul won't get it, I use a wedge, and if a wedge won't get it, I use a chainsaw. Most of the time I use a standard 6 lb. maul with a fiberglass handle. I don't even know what kind it is, but it has a pretty nicely shaped edge, not too thick right away. I've tried the monster maul and found that I couldn't develop enough speed to split difficult pieces. If it would start in the piece, great, you just have to let it drop, but otherwise it just bounces off. Gave it away. I also have a Helko Tomahawk. It is excellent on wood that is easy to split. Much easier to swing, and if the round is within its capability you get a nice crisp split that feels like a perfect 5-iron. If not, though, the maul bounces off with an unpleasant shock. I really wanted to like it because it was a birthday gift from my wife, and for a while I kept the Helko and my 6 lb. both at the woodpile, using the Helko until it bounced, then reaching for the standard. After a while I found it more efficient just to use the standard and have more pieces split the first time. I now keep the Tomahawk inside for splitting kindling down to hatchet size.
So, it's still a standard maul, splitting mostly oak and locust. I may try a Fiskars, but after the Tomahawk I'm a bit leery of anything that operates on the light weight/velocity principle. Kind of like bullets; if all you shoot is varmits, a .223 is perfect. But sometimes you need mass AND velocity, and at the moment I'd say a 6 lb. maul is about the right balance of the two for me. I'd also like to try a Stihl or Husqvarna maul, except for the price.
Jack