It depends on your area of intrest and the field you are choosing. If you want to have more practical knowledge and less theory, then you may choose Diploma. If you believe you can study and understand the concepts by learning then you can pursue ur 11th and 12th and then you can go further.
The main difference between both is that if you choose diploma then you have no other choice and have to work in that particular field. The advantage of choosing higher secondary ( 11th & 12th) is after completing you may still have various choices to continue your further education