Something else to consider are the optics. A 2" fl. lens can vary from lens to lens. Anytime you replace the lens, check to see where the true focal point is. If your new lens has a focal point that is 1/16" different from your previous lens' focal point, you will see a tremendous difference in performance. Think of the difference in processing speeds and effect when the spot size at focal point goes from .005" dia. to .0065" dia. And a full 1/16" in difference in focal point could result in a much larger difference in spot size.

On the ULS machines, you can reset your focus guage to match your true focus point. It is pretty easy to find the focal point of your lenses. Place a tongue depressor on the table. Raise one end so it is just below the bottom of the lens mount, and the other end is down on the table top. Run a vector line along the length of the tongue depressor using just enough power to mark the tongue depressor. You should see an hourglass looking mark on the tongue depressor, where the vector mark starts out of focus, goes through the focus point, then out of focus again. Leave the tongue depressor where you marked it and run the head over to narrowist part of the mark and put your focus guage at that point. The focus tool has a set screw in the base, which will allow you to change the length of the focus tool to match the true focus point. Now, if you use autofocus, you will also need to reset the autofocus setting to match the true focal point.

And we won't even get into the difference in mode quality from laser to laser.