The H1-B also need to be renewed (even for the same employer), except it's on a 4 year period IIRC. Also, the TN can be renewed indefinitely, whereas the H1-B c

The H1-B also need to be renewed (even for the same employer), except it's on a 4 year period IIRC. Also, the TN can be renewed indefinitely, whereas the H1-B can only be renewed so many times before you're "forced" into a Green Card. It can also be used, like you mentioned, as a bridge to start working immediately without having to wait for H1-B openings the be ready.