Each uniform has its place. Here are my opinions:
Mid-Late "The Original Series"
- obviously the one that started it all, while not practical, I am fond of it
Star Trek: The Motion Picture
- a terrible idea, they look too antiseptic and impractical
Star Trek II: The Wrath of Khan "Monster Maroons"
- these look much more like a formal dress uniform, only to be worn at State dinners, etc.
Later Maroon Uniform (Earlier flashbacks in TNG)
- same as above except someone forgot to put the collar/undershirt on
Mid-Late "The Next Generation"
- similar to modern Class A uniforms (A Few Good Men courtroom scene for civilians)
Early "Deep Space Nine" & "Voyager"
- similar to BDU (Battle Dress Uniforms such as worn in Iraq/Afghanistan today)
- these have much needed, practical POCKETS!!
Mid-Late "Deep Space Nine" and "First Contact"
- these are my favorite uniform as they look more like a real military uniform with the black/grey scheme instead of bright color
- similar to most Class A Navy uniforms
- a good bridge between current NASA shuttle uniforms and USS Kelvin era uniforms
- pockets make them practical
Star Trek (2009)
- I am please that they honored TOS by only slightly altering the uniforms from the original idea with modern updates