teufel hunden, I'm not sure where you are located but if you are close by it would be great to have you come shoot a few shots. I have some bows on sale right now and the deals are good. Private message me or call 814-662-4321 to find out more about the specials if you are too far to drive.
I hunted with the Shadow UL last fall and I dearly loved that bow. By far the best crossbow I have hunted to date. That being said I have to say that I would likely choose the FX4 for this season. I feel the advantage in speed would be worth it.
Let me explain why: You will need to use a speed dial scope and set the bow up so that your first crosswire is dead on at 20 or 25 yards (depending on your setup) then move back to 40 yards and adjust so your second wire down hits dead on. The distance between your first crosswire and your second crosswire will be less than 10 inches apart at 40 yards. The kill zone of a whitetail is basically a 10 inch circle. You now have a very effective rangefinder in your scope. If the 20 and 40 crosswires fit in the kill zone, you just need to adjust them up or down and pull the trigger. Using a rangefinder is still the best method and I highly recommend using one, but if you have a deer rush in or forgot your rangefinder you now have an effective system that works. This is the advantage in shooting a faster bow.