Is placing <script> tags in just before closing the <body> tag the same sa placing them in the <head> section and specifying a defer="defer" attribute?
Yes/No.
Yes because placing the defer tag waits until the document is loaded before executing.
No because placing the <script> before the </body> tag doesn't necessarily mean the document is completely loaded as you can have other tags between the closing body tag and the closing HTML tag. Example
<html>
<head>
</head>
<body>
<script>...</script>
</body>
<link/>
<script>
although it is invalid HTML most browsers will render tags outside the body. This is
probably more of an error in code
<div> some content</div>
</html>
Also of note, the defer attribute of the script tag is not functional in all browsers.
Edited:
In regards to performance for faster loading pages you may want to look at this article it provides some guidelines including where to put script and css