As a carpenter, something I came across during bathroom remodels was corrugated drain pipes underneath a sink or vanity that someone had tried to replace themselves.
Sink drains and drain pipes are fixed locations. When you alter either one of those locations, often, the old connection pipes won’t work. Professional plumbers carry every variety of these pipes. For the average homeowner, it’s hard to even imagine what pipes you’re going to need.
Flexible pipes can be a great solution, but if they’re corrugated, they’re prone to clogging. Plumbing code (and common sense) tells us that the inside of a drain pipe should be smooth. So, if you’re not going to hire a professional to install your new sink and don’t want to figure out the right combo of connection pipes on your own, make sure you buy a flexible pipe that has a smooth interior. (For example, Snappy Trap makes the approved kind).