Placement of amsthm's proof and theorem environments

Since when I started LaTeXing I've always wrote the proof environment inside the theorem, but I see many templates or answers in which first the theorem is ended and then the proof is begun.

Namely, what I am used to do is

\documentclass{amsart}
\usepackage{amsthm}% should anyway be loaded by amsart class
\newtheorem{thm}{Theorem}[section]

\begin{document}
\begin{theorem}
Statement of the result
\begin{proof}
Proof of the result
\end{proof}
\end{theorem}
\end{document}


whereas I see most people rather writing

...
\begin{theorem}
Statement of the result
\end{theorem}
\begin{proof}
Proof of the result
\end{proof}
...


I was wondering whether one is a better practice than the other (for spacing/page breaks/references...) or if it is really just a matter of taste.

• Thanks @Andrew, I added a MWE. I understand your point, but my thinking is that the proof is part of the theorem, and if, e.g., I define a command inside the theorem it would be reasonable to being able to use it also in the proof, while without nesting it wouldn't be the case, since the command is 'lost' after \end{theorem} – AndreasT Jul 13 '17 at 10:20
• The proof environment doesn't belong in the theorem environment. – egreg Jul 13 '17 at 11:08
• The theorem environment provides formatting for the statement of the theorem. The proof environment provides the formatting for the proof, which is usually just the "opening" Proof and a symbol that marks the end of the proof. The statement of my theorems are usually in italics, so I definitely don't want to put the proof environment inside the theorem environment. – Andrew Jul 13 '17 at 14:25