One thing to remember is that if you push a slow film or pull a fast film, you will change the grain and tonal reproduction. For some shots that will be the effect that you are after.

But if you are just pushing or pulling to achieve the right shutter speed or aperture, you are usually better off using a film with the correct speed to start with.

If I am shooting daylight scenery in spring/summer I would not use 400 film or set my DSLR to 400. I'd use ~100 in both cases.

On a recent trip to Madeira, I kept hitting the max shutter speed of 1/1000 despite stopping down and pulling the 400 film to 200. I'm unhappy with most of those images. The only thing I can think of is how it would have looked with FP4 (I was unable to stock up).

Some analogue cameras tend to be less accurate the higher the shutter speed. This is a good reason to keep shutter speeds in the lower half. As you'll be more certain of your exposure.