Tubes have the edge for me as they are easier to use, but liquids are okay.
Flavors
The current slightly sweet probably would work best for most people but I do love that Devil's Chocolate Cake

Colours
I can't wear warm or very neutral (eg. browny) shades

Glossiness
I like satin/shiny. Basically a happy medium - no matte or semi matte but not plastic looking shine either.
Texture
Other than colour this is the most most important factor for me - must be as smooth and moisturizing as possible. I like the colour and smoothness of some of the lipglosses- Seedy, Berry Nice, Damsel etc, but need the moisture of the clear Black label or Bad girl balm

Lasting time
Anything from 2-3 hours I consider long lasting for glosses since I drink water pretty much constantly. I like it if there's a slight stain of colour left, just so I don't need to reapply the gloss straight away.
Plumping
Given the choice I'll always choose a plumping lipgloss over non plumping. I could use that extra ooph

ETA: Thanks for asking this Karen, I'm really enjoying reading everyones suggestions and ideas
