Now that's what I call a question...
What is correct form?
Ask ten people and I expect you'll receive ten different answers!
In fact, the reason why we have differences in the performance of kata across style is ultimately down to what is considered 'correct form', which is in essence a human construct.
After all, karate doesn't really care what style it's from!
So let's take this idea of 'correct form' and explore what it may actually mean...
'Form' in karate is ultimately a result of two important aspects...the contextual goal(s) of practice and the optimal expression of human movement (under the constraints of the training environment) to achieve those goals.
This is no different to any physical pursuit, the only difference being that when goals are clear, the form becomes driven towards a more common looking outcome. For example, most people will swing a golf club in a similar way. Most people will dead lift a weight in a similar way, most people will swim in a similar way and most people will throw a dart in a similar way. The list could go on forever.
Even the use of similar tools can still bring about different 'form' depending on contextual goal. For example, look at the differences between something like speed skating and figure skating. However, when it comes to karate, we see that form can differ quite dramatically from style to style. So, it's important to consider why for instance we don't all perform the same kata in a similar way, especially if it is derived from a single source and for a specific reason! The tool is the same (the human body) for us all, therefore it stands to reason that the biggest contributor to form in our karate should be the specific goal(s) we aim to practice for.
One of the best things about modern-day karate is that the art has become malleable to suit a range of valuable goals. If you want to become the next WKF champion then there's a route for you. If you want to focus your attention toward civilian self-protection and the practical application of kata, then there are plenty of dojo around now for you to explore that aspect. If you want to align closely to history and tradition then many schools offer that too. Even if you don't care so much about the physical attributes and instead simply want a means to offload the stresses of a hard working week, then karate has also an answer for that. And given the change in emphasis of karate since leaving Okinawa to mainland Japan and then to the rest of the world, it's no wonder why we see so much variety of form.
But let's think about this for a moment...
What we are saying here is that the 'correct form' in karate is all based on the context with which we practice and thus relies on two critical standards...
It's quite a common way of thinking in karate that one should aspire to leave behind 'aesthetics' to emphasise 'function over form'. Although I agree that we should strive to adapt to a very personal way of applying our karate, I do however also believe that adherence to form is very important and the problem usually lies with not the retention of form itself (or lack of it), but instead, the way many karate-ka define the term 'form' and as a result, mistakenly differentiate it somehow from function. Form and function are not at odds with one another. In fact, they should holistically complement each other!
In application, 'good form' will be different depending on what goal you're working towards. That's why when performed, kata primarily studied for competitive success and kata primarily studied for functional success in self-protection may look and feel very different! But who is right? Well if they satisfy the above two standards, then they may BOTH be right!
Form as a product of context relies on the universal structural and dynamic components of the human body. Because that is the tool we use to express our karate! Therefore, I believe that form defined in this way should never be discarded. But this doesn't mean that we cannot express our individuality via the baseline platform provided to us through good form. Individuality in karate should not be thought of 'instead' of form, but rather, a quality that enthusiastically embraces form. This is why for me, the term 'function over form' has become a nonsensical ideal, because there can be no effective function WITHOUT contextually correct form!
Let's take a simple example of wrist alignment in a strike. For a technique such as choku-zuki (straight thrust), it would be considered good form to make sure that your fist lines up directly with your forearm in order to minimise the chance of the wrist buckling when delivering impact. Kink the wrist only slightly in 'determined application' and there may be very painful consequences. In the photo below, I would opt for Image A being 'better form' than compared to Image B every time!
Ok - let's change the technique now to uraken-uchi (back fist strike). This technique is performed in a different way to choku-zuki and to create a whipping strike, dig in with the knuckles and help protect the possibility of impact against the small bones on the back of the hand, additional wrist extension would be beneficial. Therefore in this case, we could say that Image B would be 'good form'.
So, different applications using the same part of the body require a different standard of form. Do you believe that we should simply abandon this form for the sake of individuality and maybe employ choku-zuki in accordance with Image B and uraken-uchi in accordance with Image A? Of course not! This is why 'correct form' (so long as it's derived as a result of your contextual goals) should always be pursued.
If 'correct form' comes from the result of working toward specific goals and conforms to optimum human movement principles (using your tool(s) in the best way possible) then there would be no need to abandon form for function, as they would both interlace perfectly. I think the problem occurs in karate when we try to use Form A to meet Goal B, as in this case, form may not align at all to function. It's not that the form is incorrect (compare wrist alignment images above), but in trying to fit a square peg into a round hole, the answer is not to mindlessly squeeze it in for the sake of conformity (we tend to see this a lot in karate). Instead, our peg (form) needs to become less 'square' and more 'round'.
So I wonder...what is YOUR correct form?