To compare stack call speed across platforms like BricsCAD, AutoCAD, CADian and ProgeCAD, you need to create equivalent recursive functions on each platform and measure their execution time. This can be done by using the timer function to measure the time it takes to complete each function.
(defun test-speed ()
(setq start-time (get-internal-real-time))
; code to test speed goes here
(setq end-time (get-internal-real-time))
(princ (format "Elapsed time: %f seconds" (- end-time start-time))))
In this example, the test-speed function can be used to measure the time taken by the code that you want to test. The get-internal-real-time function returns the current internal real time in seconds and the format function is used to print the elapsed time in seconds.
As for your other questions, the speed of stack calls inside VLX or FAS files may depend on various factors such as the size of the file, the algorithm used, and the specific implementation of the programming language. It's difficult to say which one is faster without further information.