8th vote for 1UP. One consideration not mentioned yet. Colorado sun kills rubber and plastic bits over time. 1UP is all metal.
[MENTION=511698]redmartin[/MENTION] mentions fat tires. Standard 1UP just barely fits my 3" Plus mtn bike. Any wider would need the wide tire solution.

I like that it's compact in it's solo configuration (my usual) but that a second carrier is easily installed. Not applicable to OP but if he ever wants to carry a third bike, that's also easy to install.