Pressure Cooker vs. Slow Cooker for Moist Meat
If you are using the wrong kind of meat (= tender meat low in connective tissue), the pressure cooker will make it much worse. With this meat, the more energy goes into it (and the pressure cooker gives it more over the same amount of time), the worse it gets. You really have to prepare it as a steak or roast. 

It would be an interesting thing to try out on the right kind of meat though, since there you want to break down the connective tissue, and the pressure cooker could be better at it.