Sony 70-350 or the Tamron 70-180 full frame on a Sony 6700?

I'm looking for a telephoto zoom lens to complement my Sigma 18-50mm f/2.8. I take photos of my family, nature, travel, etc

I understand that the Tamron 70-180 is a FF lens, but the constant f/2.8 across the entire zoom range is enticing. Right now, both lenses are the same price.

How do I weight the pros and cons here?