But -- they both take time.
The TBR pile can be a form of vacuuming the cat. So can the books from the library -- which, come to think of it, are generally worse. Sure, you have to return them to the library (unless you renew them) so they aren't hanging around. Then, by the same token -- you have to return them to the library! So you have a deadline. So to speak. . . . It does help with the gentle art of not reading books that don't interest you all the way through if you realize they are due.
Discovering new authors, particularly ones that have written several books by the time you lay hands on them, can be a horrible time sink.
Restraining how many books I get out of the library is the only trick that really works, and since it's very hard to remember that while actually in the stacks, I have to restrain the number of visits, too.
(And this without getting into reading as research. . . .)