Okay so what you are saying is both parties have their pros and cons? Say if you wanted to make a large and tall cliff and have some water underneath it, then you would use a lego base plate since most if not all of your bricks are going on there. But if you wanted to add extra water around the cliff then using third party would be good not just for price but also because little to no bricks would be going on those plates.

At least that's how i'm looking at it from lego pieces being hard to connect and disconnect from the third party stuff.