Another vote here for the Fiskars X27. Before buying one a couple years ago I used an old school long handled maul almost exclusively for the previous 45 years. Since then the mauls have been demoted to driving wedges for the odd piece that's to big or gnarly for the X27. About all we burn is red oak.
From what I've gathered in threads about the X27 vs. the various mauls, preferences seem to depend on your splitting style. If, like me, you hold the handle as close to the end as possible and take a full swing, with your arms at full extension as the tool's head goes over your head, I think you're more likely to prefer the X27 over a heavier maul. I'm 5'-8", 140 pounds, and 72 years old, so the long arc allows me to maximize the kinetic energy in the head with minimum effort. A stronger person may like a heavier tool and a more truncated swing for the easy splits, and save the full swing for the tough stuff.