What do you need to cart around daily, and how big is the campus?If 99% of what you do is tuning and regulation touch up, just bring a small bag with your basic tools. If you do specific repairs regularly, bring those tools as well. If you're talking about carting around your entire non-bench collection of tools because your regular jobs are so varied, you might want to go for a cart of some kind.
If you only bring specific tools, and you happen to need a different one, is it possible to come back the next day, and today move on to the next piano? Or would it really hinder your schedule to not carry everything?
My philosophy regarding carting around tools has always been, you only get one body. Don't abuse it if you don't have to.
I really like the Versacart. I've just bought it for a third time, since my first, beat up and tossed around and used over and over again, began to feel its age after 7 years. So I changed to the spare, and then bought myself another spare, because I never want to be without it. Now that I'm old and walking slowly with a cane, I find that I can walk two or three times faster leaning on it, as it carries everything for me.
It holds a lot of weight (rated for 120 pounds), and it folds up so I can just toss it into the back seat. It holds any number of things. There is a flap with velcro to keep out rain or snow. My folding action cart can hang from the handles, which was a deal-maker the first time I bought it.
Not very good on flights of stairs, but one or two at a time are no problem.
The price, alas, keeps going up.