there is one huge advantage to the 'forth' way of doing things, you can start processing left-to-right as you read in the data. This makes it possible to stick a forth 'processor' on the other end of a wire and to parse / run the code as it gets pushed down the wire without needing backing store the size of every possible input.

For a 'lisp' like structure you'd need at a minimum enough storage to get all the way to the innermost expression before you can start to interpret the data.

Normally not much of a problem, but if you were to make a fabric that consists of little processors stuck together with comms wires the forth way of doing it could be an advantage.