The main difference between things like the Roughnect maul and the others mentioned above is the profile of the blade. The cheap mauls have a straight profile whilst the Splitting axes have a curved profile. The curved profile allowed greater initial penetration and then ramp up the splitting pressure as the axe penetrates further.
From teaching both kids and adults to chop logs the Fiskars are an excellent splitting axe. It is by no means my favourite, but it takes a lot of abuse, is very robust and is every efficient. I know a lot of people do not like the plastic handles, but when they get left out for a couple of weeks you soon learn to like them not splitting, swelling or giving you splinters.
Now for the pewrsonal preference then it will always be a Granfors Bruks splitting maul, but the price is eye watering now. So I would get the Fiskars x25 if the logs are going to be big or the Bahco splitting axe with an ash handle if you prefer the wooden handle.