Technically, there is a difference. "下さい" is "Please GIVE me xxx" 飲み物を下さい。Please give me a drink. In this case, YOU are trying to GET something. "ください" is an honorific expression, which can be put after verbs. お飲みください。Please drink it. 食べてください。Please eat it. 書いてください。Please write it. I think these two words are sometimes (or often?) used without any distinction even in business situations. But some people pay attention to their usages. The following is a site for this explanation, although it's in Japanese; just so you know. http://matome.naver.jp/odai/2140253271086927801

I see ください written as 下さい often so i believe it's right, and i think you can use both. I'm also learning though, so others may have different opinion

You can use both, but you don't need to use kanji for kudasai. Actually, many publishing companies and newspaper companies recommend ください, not 下さい. There are no strict rules of using kanji. But those companies and official organizations usually have their own guidelines for readability.

Yes, ください is written as 下さい in kanji. I Typed たべてください and got this result: 1. 食べてください 2. 食べて下さい 3. たべてください 4. たべて下さい However, I think it depends on your past entries. For example, if you always select 食べて下さい, it will appear as first choice.

Two learners gave you a good answer, however I completely agree with Jun-san.