Comma first seems more consistent to me.... unless you write your WHERE clauses like this:
WHERE a=b AND
a=d AND
e=f
Because it makes your SQL more legible.
In english, commas go after the previous word, not before the next word. The syntax is the same for all programming languages. The fact that most compilers and interpreters don't require it is not an excuse for abusing it.
Besides the subjective argument of legibility, what other benefits does it have?
Having a comma preceding something is an indicator that it is one of many. When debugging you can easily comment out the column, or table from a query.
And I personally prefer the rest of SQL to be in lowercase, so it does not attract too much attention. Usually in SQL table names and column names is the most important information.