Here's the way I consistently cast my vote:
In-room workout equipment (free weights, yoga mats)!!! ^
I think the courtesy Internet would be far more universally appreciated and used by frequent business travelers, but when I'm working in my room there's nothing like being able to pop up from behind the laptop and burn some nervous energy on a treadmill or with free weights or a decent abs cruncher!
I find that when I'm able to take frequent
"nervous energy breaks" I'm much more productive, feel great and sleep like a rock.
The Westin
"in-room gym" is amazing, and I always opt for similar options at other hotels. (Ritz and Four Seasons are offering them more consistently outside the USA). I'm surprised that all chains don't make it available system-wide. The joke is that if they offered workout equipment in-room, most guests would grab the offer and be content to pay for it, or readily accept the workout equipment as a perk and happily pay for Internet anyway! (At least I would).
The in-house health clubs are great, but when you're working late into the night it's wonderful to be able to take a 15-30 minute exercise break in your room every couple of hours!