I vaguely seem to recall reading that \newenvironment* gives better spacing than \newenvironment, but I don't recall any details and I can't seem to find a reference by searching. What is the difference between these two, and when should one be used rather than the other?
[Note: I'll be happy for this to be closed as a duplicate, as long as someone can point to the question of which it is a duplicate; I cannot seem to locate such a question.]
The relation is the same as that between \newcommand and \newcommand*, which is covered in What's the difference between \newcommand and \newcommand*?
There's no influence on the environment's behavior, except as regards to the arguments to \begin{envname}.
Specifically, if you say
\newenvironment{foo}[1]
{something with #1}
{something else}
you're allowed to say
\begin{foo}{An argument
with a blank line}
The environment's contents
With perhaps a blank line
\end{foo}
while \newenvironment*{foo} wouldn't allow this and the argument should not contain any blank line (or \par command), but the environment's contents has no limitation (other than those possibly imposed by its definition).
\newcommandand\newcommand*: if there are arguments to\begin{foo}, then they are allowed to contain empty lines in the former case and aren't in the latter. See http://tex.stackexchange.com/questions/1050/whats-the-difference-between-newcommand-and-newcommand – egreg Dec 10 '12 at 21:25foo, then using\newenvironment*rather than\newenvironmentwill have no effect on what is allowed in between\begin{foo}and\end{foo}, but will have an effect on what is allowed inside arguments to\begin{foo}. And there is no effect on spacing. Is this correct? – Charles Staats Dec 10 '12 at 21:34