Which handbag/messenger bag/briefcase/luggage brands are the most popular among business…?

You cover a lot of ground–messenger bags, briefcases, luggage, and handbags. And, you don’t specify male or female executive.

At a high level, I would agree with you that Tumi is definitely a popular brand for many executives, at least over the past 10-15 years. Previously, you had brands like Hartmann and Atlas cases.

It is relatively easy to see a large spectrum of bags for male executives. In the era of portable computers, these all need to be able to carry laptops. Tumi is certainly top of mind. If you want to see where I have gone to shop for many years in NYC, go to this website:
http://www.crouchandfitzgerald.com/

But, finding a good quality, functional, and fashionable “briefcase” for women executives is harder. Take a look at these websites:
http://www.mobileedge.com/products_her.asp?cid=6&scid=6
http://www.squidoo.com/laptopbag

As for handbags, I won’t even go there. There are dozens sold by each of 5 stores on almost every block of NYC. I would imagine a female executive on Madison Avenue (advertising industry) or in the cosmetics or perfume industry would employ different attire from executives at banks or lawfirms.

Luggage is also full of options. Tumi and Hartmann stand out. There are of course numerous high end brands. Go to the above Crouch & Fitzgerald site.