fruitcakes can be moister or dryer - adding to that,,, they have more or less "stuff" scattered through the dough.
a moist fruitcake with lots of chunky stuff is less good at thin slices.
a drier cake - lots of flour in the recipe - with minimal fruits/nuts is apt to slice thin without breaking.
leavening is another thing - baking soda makes for denser than baking powder; or a combo of both.
I have a recipe that produces a 6 pound (96 ounce) fruitcake; uses 1.5 cups ~ 7.5 ounces of flour - and a cup of booze.
it's moist; you kinda' hafta' bake the recipe and see if you like it - "predicting" can be tricky because fruitcakes also use butter and eggs and sugar and and and ... which all affect it's texture.
