Lufthansa have now cracked down on cabin baggage with an 8Kg limit - any wheeled bag eats into this allowance. You are allowed a laptop bag in addition to the carry-on.

I vary my carry-on bags - though I'm currently using a mix of:

eBags Motherlode Wheeled Duffle when I am allowed a heavier bag or mayy want to check it
eBags Weekender when I want to go wheels free
eBags Professional Weekender - works well as an all-in-one overnighter plus a carry-on when I have a checked bag. The size allows me to ensure it goes in the overhead and not steal my foot space

I also have an Eastpak messenger which I sometimes stow in my main carry-on to shuttle stuff to/from the hotel to the office.