JavaScript variable definition: Commas vs. Semicolons

What are the differences and/or advantages, if any, of using commas when declaring a group of variables rather than semicolons.

For example:

var foo = 'bar', bar = 'foo';

versus

var foo = 'bar';
var bar = 'foo';

I know that if you specify the var keyword on the first variable in the first example it persists across all of the variables, so they both produce the same end result regarding scope. Is it just personal preference, or is there a performance benefit to doing it either way?

No performance benefit, just a matter of personal choice and style.

The first version is just more succinct.

Update:

In terms of the amount of data going over the wire, of course less is better, however you would need a hell of a lot of removed var declarations in order to see a real impact.

Minification has been mentioned as something that the first example will help with for better minification, however, as Daniel Vassallo points out in the comments, a good minifier will automatically do that for you anyways, so in that respect no impact whatsoever.

After reading Crockford and others, I started to chain my variables with comma exclusively. Then later, I really got annoyed by the Chrome DevTools debugger that wouldn't stop at variable definitions with comma. For the debugger, variable definitions chained with comma are a single statement, while multiple var statements are multiple statements at which the debugger can stop. Therefore, I switched back from:

var a = doSomethingA,
    b = doSomethignB,
    c = doSomethingC;

To:

var a = doSomethingA;
var b = doSomethignB;
var c = doSomethingC;

By now, I find the second variant much cleaner, not to mention its advantage of solving the debugger issue.

The "less code through the wire" argument is not persuasive, as there are minifiers.