INVASION

It's genuinely exactly as other comments have already said: if you don't have a full health bar before the final rush, it becomes so much harder to survive the ending. It took me three attempts, but on the third run I super focused on making sure I made it through the bracket long-notes with full health- it was enough to let me barely scrape through the very final run. If you have great foot speed, you might have to worry less about this (I absolutely do not have great foot speed)

If you leak even a little bit of the holds in the second half, it's easy to die in the late spike run that follows.

You need a full gauge from the tree to survive.

On the other hand, the special song in the variety pack has the fastest BPM, includes holds, and has a moderate amount of brackets, but the runs are short and can be handled decisively.