You shouldn't use a power drill when precision is required for drilling holes or tightening nuts and bolts. Impact drivers are designed for use in specific applications, where drilling isn't necessary but the impact action and increase in power aren't known for leaving behind the finest finishes. Because they're powerful, you don't want to use them for tasks like tightening nuts and bolts, which require precision. Even though they're less powerful than impact wands, there's still the possibility of over torquing and stripping threads.