If you think you have a better design in mind than the MP piece or the Milodon piece then go for it.
If you're trying to save weight, it's not that significant.
If you're trying to save money, it's your time and sweat.
Be careful of the thickness of the aluminum. If it's too thin it might crush,warp,deform at the flange when you try to snug up the oil pan bolts.
FWIW, the price of the aluminum one seems to be more expensive than the MP or Milodon. In that case, I will stick with steel. Plus the MP one includes 2 oil pan gaskets.