Discuss Cells from The Dark Descent here.
It seems like it's merely a few frames faster to use a potion in Cells as your movement speed will be 4.25 instead of 4.05 and rising (up until it caps out at 52 when you're at the final flight of stairs). In other words, save your potion for later. You will take damage in the later maps, so it's recommended to keep it until Inner Sanctum. Comparison video for the in-bounds route.