准备：prepare, intend, plan, arrange, fix, be ready 打算：contemplate, figure on, intend, plan, propose, set out, think

准备 means "prepare for ..." 打算 means "plan to..." "Are you ready?" means 你准备好了吗？ In this sentence, you only can use 准备.

准备 means 'be going to do ' 打算. means 'plan to do '

i think ,the difference is ,准备means getting ready and going to do,if you say 准备 doing something ,that means you will have the action,and you will do. and 打算just means you just think about to do something, but maybe will not to do ,that just is an idea,a plan.in a word, 准备,you must to do ,and 打算，you will do ,or not ,that's all right. hope this will help you,will not make you puzzled~

差别不大。你用这两个词写句子，看看有没有毛病吧