I plan to upgrade my Makita impact drill to DTD171 as well. Most trade-end Makita impact drivers are durable and reliable. It survives rain, dust and drops. I dropped mine off a 4m high scaffold straight onto concrete more than once but it still works to this very day. It simply won't die.
However, I cannot guarantee how well these new generation of Makita drivers fair on drop tests due to increased on-board electronics and switches. I can guarantee the transparent plastic nose ring and its glow-in-the-dark rubber are the first things to go on a rough job-site environment; only affects the look.