"Please note" is more polite. It's possible to interpret "please pay attention" as a reprimand. And since there are less verbal clues in written correspondence, it's best to avoid misunderstandings.

I don't think there is any major difference between these two sentences, but if I were to write the email, I would use "please note that" rather than "please pay attention to the following." I feel "please note that" sounds more professional and polite.

"Please note that....."? Sounds a bit better, a bit more friendly kind of formal Feel free to add me as a friend if you need more help as your buttons don't work ^_^

I appreciate your attention is more polite.

It's not very polite, and as stated earlier it might lead to Big misunderstandings. you might try capitalizing the portions of your email that you feel require more attention