A Sharkbite fitting relies on an O-ring to make the seal. To keep that intact, the end of the pipe must be smooth without any burrs or sharp edges. And, the pipe must be nice and round without scratches or dings. Once installed, the thing holding it in place are stainless steel spikes. As a result, it doesn't take a huge amount of force to rotate the valve, but pulling it off is tough unless you use the release. Given the choice, a compression valve is probably still the best choice, with a soldered one next, then a push-on valve like the Sharkbite. The first only requires simple tools (a pair of wrenches), while soldering requires a torch, solder, flux, and something to clean up the parts prior to soldering and some skill.
Note, not all valves of any type are created equal...some are better than others. For the most part, you get what you pay for within a type.