In some ways, they are, in others, no. I went to a loosely uniformed primary school (polo shirt, skirt or trousers, school colour jumper) for three years, then a non-uniform primary school for four years, currently in a strict uniform high school (blazer, tie, shirt, skirt or trousers (all in school colours, with logo)) and I'm planning on going to a sixth form college with no uniform, so I've experienced a range of things, uniform-wise.
I'd disagree with the statement "uniforms discourage bullying" - differences are highlighted if you're all the same in every other way. You can stop being "the kid with the Mickey Mouse jumper" by wearing something else, but you can't stop being "the ugly girl with the funny shaped nose" or "the dumb boy with dyslexia".
Uniforms can look smart - although teachers at my school are constantly telling the class that their uniform is wrong (e.g. tie knot is too low) and they look very scruffy. This wastes class time.
I also don't entirely agree with the idea that they suppress creativity - kids try other things, like showing their personality through their actions, on the plus side. Unfortunately, there are bad outlets too - things like drinking and smoking as a way to stand out. I read that girls at uniform schools tend to start wearing make up earlier than other girls. My point is that kids will always express themselves - just not always the way adults would like them to.
I've noticed that girls tend to roll their skirts up and act older as a way to be individual, putting themselves at risk of unwanted attention (I often see little girls of 11 or 12 years old at my school, with very short skirts, flirting with boys my age or older... it's pretty easy to guess what the guys are thinking and it makes me worry if the girls know what they're letting themselves in for).
Dress codes, I guess. But there would have to be boundaries - along the lines of "something you could wear around an old folks home without shocking anyone" (i.e., no racist/sexist/etc slogans, no short skirts). Or, if they wanted something a bit more smart, maybe a smart-casual or business style dress code.
If a uniform is for safety regulations, I'd say to stick with it - for example, a PE uniform - it would be pretty dangerous to sprint in heels. Maybe just an "appropriate for work" dress code - like if you did woodwork, you could wear overalls.
I guess subcultures would be more visible - it's a kind of uniform in itself, if you think about it... I've noticed that on non-uniform days, kids seem to cluster towards the same kinds of clothes. I notice parallels between my clothes (hoodies, baggy jeans, t-shirts) and the clothes of friends at the non-uniform sixth form I want to go to even though I met them when they were at my school wearing uniform and they've never seen me out of uniform, we still dress similarly in leisure time. People tend to have a small selection of types of clothes they wear - it's unlikely that a girl like me would wear heels and a floral dress from some high end shop and it's equally unlikely that one of the popular girls who shop at Hollister would wear their older brother's jeans.
In some ways, it could be dangerous - I know that there are people out there who'd smuggle knives and whatever else into school if they had somewhere to hide it - with own clothes, it would be easier to conceal stuff, because officials wouldn't know all the hiding places in any one piece of clothing.
Initially, people would be cliquey about it, but the same was true in my first two years at high school, because wearing ties and shirts was foreign to everyone. Nobody was really confident, so they judged each other on how they wore their uniform as a way to make themselves feel better about themselves. I think that the bullying over what people wore would wear off after a bit, 'cause people would get used to seeing people in non-uniform.
I think it would free up class time as teachers wouldn't have to reprimand students on their clothing, however, there may be some etiquette issues that need to be addressed (e.g., wearing hats indoors is considered rude by some people).
Also, there are very few jobs that allow people to wear whatever they like, so it may be something of a culture shock for school leavers entering the workforce.
I'm a teenager. Also, I tried to explore both sides, because I don't think it's clear-cut good or bad... ended up rambling a bit!