I would say unless you are a really light packer, don't go less than 20" I've got a 20, but also generally bring a backpack with food and a computer.

I think the two most common brands are travel pro- 20-22" for around $200 and the expensive one purdy neat for around $280 (22"). Both will do you well and stand up to most beatings.

One brand that is standard issue for FAs at my current company, I chose to buy my own because they offered a discount and its a good bag is e-bags. www.ebags.com You'd want the ebags Professional 20" upright. I've had it for a year and a half now, still looks brand new, wheels roll very well.... basically I like my bag. Its $139 on their website, but if you call you might get a airline discount, who knows, always good to ask.

Recommendations: Size 20-22" Brands: the three mentioned, do not go to a department store and buy regular luggage, it will only last a month. Happy shopping.