I've never been big on the TOS uniforms. Their design was utterly unconvincing in that they represented a large fleet of the Federation. I'm not the only one with this opinion:

Pajamas don't belong on the bridge. If I had to wear these, I'd resign my commission:

Then Robert Fletcher got it right, I believe with Nicholas Meyer's direction.

Hooray, Starfleet officers can finally travel the galaxy with dignity and other civilizations can take them seriously when they talk about the "Starfleet uniform code of conduct."

The TNG uniforms started out as this, and something was seriously missing:

Starfleet revised them a bit during the third season by putting in collars and made the senior officers look more official than the lower-level schmucks who were stuck wearing the older uniforms for a while so the aggressor alien race can easily pick out who the expendables are.

In "Yesterday's Enterprise," they revised the uniforms just a little more with a solid collar front ... but wait, then they decided to remove the white turtleneck for the 1701-C-era design. There's something really incomplete about this look, especially when the belt is missing while the back loop for it still exists. Was the Federation in an economic recession at the time or something?

Picard couldn't even bring any dignity to it in "Tapestry." Someone needs to be fired for this.

While on the subject of uniforms, we can't forget how zero-gravity environmental suits evolved over the course of history. Here's Starfleet's early attempt below. Apparently, there's absolutely no need to ever see outwards on your peripheral left or right in case a big alien monster is about to attack you. It almost looks like the landing party is about to go diving.

While investigating V'ger, Kirk and Spock have a chance to show-off the new-and-improved thruster suit that looks more practical, with plenty of headroom.

I don't know if these were air-tight, but the blue face shield nicely matches the return of the bright blue phaser beam. The assault phasers in "The Undiscovered Country" rocked.

Picard and company had space suits that had blinking lights, because futuristic outfits should always have stuff that lights up and electronic surfaces that you can press down on to make things happen:

Back in the 23rd century (in the new, alternate timeline), space jumps demonstrate that you have parachutes and compartments to hold neat things like folding swords. The center chute release / retract button has the bold and distinguished Starfleet delta shield that's large enough to be a Toyota logo screaming, "See? I'm from the Federation and HERE TO HELP!"