Just a note- if you're doing OCR A level RS, and you're exams are in June this year, you won't be asked this question (Q's on ethical theories like this shouldn't be asked, it'd just be more general ones on Euth. and Sexual ethics- you can check the advance information for the topics you'll be assessed on).
Honestly it depends on how you normally write essays. I usually start with an intro which explains the key ideas of any ethical theories or scholars that I'll bring into the essay (this does require some editing when I actually write the essay though, as I always think of a new scholar to add in like halfway through). Then it'll be a critique paragraph - it doesn't really matter if you're arguing for/against the statement, but I always try to conclude one paragraph for the thesis that I'm arguing for. For this question, I'd probably agree with the statement as it's the easiest thing to do. For the 1st paragraph, I'd use kantian ethics, explain it and then talk about why you'd agree with the statement, giving critiques but also supporting it throughout. Conclude with the statement. With the 2nd paragraph, you'd want to say that another ethical theory is more appropriate for making ethical judgements (you can choose which one, it doesn't necessarily have to be Util.). Again, support and critique the theory throughout, concluding that Util is better than Kantain ethics at making ethical decisions. Then conclude, quickly summarising why Util is better than Kantian ethics. Hope this helps!