They are two different genera in the same family (Cypress). Kind of like asking the difference between a leopard and a cheetah. Both are deciduous. The trees, not the cats.

What Sara said (BTW, neither leopards or cheetahs are evergreen), but if you have specific questions or ways you want the two plants compared, it would help if you could clarify, or expand on, your question.

Either species would be fine. If the area gets mowed regularly, you might choose DR, as they don't produce knees.

Egypt, I grow both and love both species. They both have their advantages and and occasional disadvantage. But if space is an issue, I would suggest the BC over the DR. Dawn Redwoods need space and grow fast.

littleegypt, there have been several exhaustive threads about these trees on this forum. Why not search for them?

You're from Illinois right? BC is an Illinois native.

Here is a pic of a cultivated planting of BC, more often than not they will lack knees, especially of not near water.

There are lovely cultivars of both, that don't grow nearly as fast, hence do not get nearly as big in our lifetimes. M. 'Miss Grace' is a weeper. There are golden foliaged versions, too!

I have actually heard of Metasequoia producing knees.

Non-dwarf (or dwarfed) versions of either become landmark trees over 60 ft. tall. So even where enough horizontal space is present nearby objects - such as houses - may eventually be made small-looking by the big tree being present nearby. Small-sized debris produced by cypress family conifers such as these can also be a bother in gutters and in pools, when these latter features are close enough to the trees to accumulate a significant amount of material.

Metasequoia "Ogon" is one of the most striking cultivars of any tree I have ever seen.

Pond cypress is pretty common around these parts, the leaves are a lot more slender, as is the whole tree. Knees are less prevalent too.

In my area we had a rainy spring and summer. As for September no rain, parched, hot and droughty. It's really dry, some broadleaved trees are defoliating and going dormant early, Here is a remarkable Bald Cypress today, not a single brown needle! The ground slopes downhill from this spot. Surely you agree it is remarkable how well this species tolerates such a wide range of soil moisture. Note: pic below, no knees.

Sam, indeed it is remarkable. Seen it growing from southern Canada (Niagara) to south Florida. Thrives here in west MD along a (sometimes) flood-prone stream where other trees can get swept away.