If you go with 9 ft in the basement and are mindful about placing plumbing and HVAC ducts you can end up with pretty close to an 8ft finished ceiling height. Combined with a couple of egress style window wells to provide big windows and natural light that turns the basement into a much more inviting, useful space at very little added cost. I wish we'd gone with 10 ft basement walls.

I'd look at the possibility of making the garage a little deeper to provide storage space in front of the cars instead of adding a third bay.

Sounds like you are building with a tract builder with specific add-on options? If so, what are other home buyers choosing? I would think the 9 ft ceiling in basement would add more value.

It depends on what 9 foot means. When I had the default 8' basement ceiling increased to 9', the underside of all the floor joists were 9 feet above the floor, but a supporting 12" beam extended down to 8', and some ducts were run which also were 8' above the floor. It is, however, an acceptable situation for me.

Yes, you're lucky to end up with a clear ceiling height of 7 ft if you pour 8 ft walls. That's very common around here, as are things that drop down as low as 6 ft depending how creative the HVAC guys and plumbers are.

A 9' pour basement clearly has a better marketing presentation for a house, as basement infers Midwest/NE cold climate where new construction basements are considered future living space, and ceiling height cannot be increased later.

A 7'x14' garage bumpout is nothing larger than a shed, where a shed can be added later, even an addition adding a full 3rd stall.

Note I used "marketing presentation" instead of ROI as too many variables on that.

A nine foot ceiling in a basement will make it more livable when finished off, a larger garage will enable you to collect more junk.

What is more important to you and your family? Will you use the basement as living space? If so, then 9' ceilings would make sense. If you have a lot of bikes, and other sporting paraphernalia to store then maybe more garage space would be a plus.

If you build it, you will fill it.

You can always put in a shed later….you will never dog out an extra foot from the basement. Go with the awesome ceiling height. Makes a huge difference.