user703: In article in wiki about chess960, it is stated that:

It has been argued that two games should be played from each starting
  position, with players alternating as White and Black, since some
  initial positions may offer White a bigger advantage than in standard
  chess. For example, in some Chess960 starting positions White can
  attack an unprotected black pawn after the first move, whereas in
  standard chess it takes two turns for White to attack and there are no
  unprotected pawns

But what are these positions? Is there a comprehensive study of some of them?

user16835: While probably all 960 positions are a draw with best play, some positions give White the possibility of entering a position that forces Black to play exact, in order to not get in material disadvantage. In other words, White can make immediate threats that must be countered correctly. You can see this page for the motives you have to look out for:
https://lichess.org/study/UQTwIHXt
These are not the only starting positions with that motive but they are prototypical.

user19648: I built this analysis over more than 4.5 millions of games played in Chess960 variant: 
https://github.com/welyab/chess960-win-by-position-setup
The most unbalanced setup is RNBKRBQN where white has 51.44% of win, and black 44.75% of win.
At general, white has a win rate of 49.17%, and black with 47.1%. There are more information on github repository.

user26472: This question was put to the Norwegian supercomputer Sesse in 2019, which analyzed each opening position using Stockfish 9 to a depth of 40.
Its conclusion was that there are four initial positions that give white an advantage of 0.5 or better. The maximum imbalance (worst for black) is BBNNRKRQ which has an evaluation of +0.57 in white's favor.




position
eval




BBNNRKRQ
0.57


NNRKQRBB
0.52


NNRBKQBR
0.50


QBBRKRNN
0.50




A side note: none of the 960 possible starting positions had an evaluation in black's favor. They're all even or favor white.
See more details in this article on chess.com.
And this report on blogspot.

user3237: I asked myself the same question a year ago.
I found this interesting page: http://computerchess.org.uk/ccrl/404FRC/opening_report_by_white_score.html#table_start
With statistics for every 960 positions based on 144,300 games played by 123 engines.
Apparently the position that gives the biggest advantage to White is RKNQBBNR with a White score of 63.9%.
Note that on the previous page the standard position has a White score of 56.0%. I once read that the true White score in standard chess is 55.5% for GM games. Since these two numbers are pretty close it would seem that the statistics of the previous page are meaningful and pretty accurate.
Also, someone once told me that if we just inverted Knights and Rooks then White would have a big advantage: NRBQKBRN.
But the previous page actually says that White only scores 47.4% in that position, so maybe he was wrong.
Anyway, I seriously doubt there exists a position where White has an advantage of +0.50 or more. And every single one of the 960 positions are very probably just draws with best play.

703: <p>In article in wiki about <a href="http://en.wikipedia.org/wiki/Chess960">chess960</a>, it is stated that:</p>

<blockquote>
  <p>It has been argued that two games should be played from each starting
  position, with players alternating as White and Black, since some
  initial positions may offer White a bigger advantage than in standard
  chess. For example, in some Chess960 starting positions White can
  attack an unprotected black pawn after the first move, whereas in
  standard chess it takes two turns for White to attack and there are no
  unprotected pawns</p>
</blockquote>

<p>But what are these positions? Is there a comprehensive study of some of them?</p>
 16835: <p>While probably all 960 positions are a draw with best play, some positions give White the possibility of entering a position that forces Black to play exact, in order to not get in material disadvantage. In other words, White can make immediate threats that must be countered correctly. You can see this page for the motives you have to look out for:</p>

<p><a href="https://lichess.org/study/UQTwIHXt" rel="nofollow noreferrer">https://lichess.org/study/UQTwIHXt</a></p>

<p>These are not the only starting positions with that motive but they are prototypical.</p>
 19648: <p>I built this analysis over more than 4.5 millions of games played in Chess960 variant: 
<a href="https://github.com/welyab/chess960-win-by-position-setup" rel="nofollow noreferrer">https://github.com/welyab/chess960-win-by-position-setup</a></p>

<p>The most unbalanced setup is RNBKRBQN where white has 51.44% of win, and black 44.75% of win.</p>

<p>At general, white has a win rate of 49.17%, and black with 47.1%. There are more information on github repository.</p>
 26472: <p>This question was put to the Norwegian supercomputer Sesse in 2019, which analyzed each opening position using Stockfish 9 to a depth of 40.</p>
<p>Its conclusion was that there are four initial positions that give white an advantage of 0.5 or better. The maximum imbalance (worst for black) is BBNNRKRQ which has an evaluation of +0.57 in white's favor.</p>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th style="text-align: center;">position</th>
<th style="text-align: center;">eval</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: center;">BBNNRKRQ</td>
<td style="text-align: center;">0.57</td>
</tr>
<tr>
<td style="text-align: center;">NNRKQRBB</td>
<td style="text-align: center;">0.52</td>
</tr>
<tr>
<td style="text-align: center;">NNRBKQBR</td>
<td style="text-align: center;">0.50</td>
</tr>
<tr>
<td style="text-align: center;">QBBRKRNN</td>
<td style="text-align: center;">0.50</td>
</tr>
</tbody>
</table>
</div>
<p>A side note: none of the 960 possible starting positions had an evaluation in black's favor. They're all even or favor white.</p>
<p>See more details in <a href="https://www.chess.com/article/view/whats-the-most-unbalanced-chess960-position" rel="nofollow noreferrer">this article on chess.com</a>.<br />
And <a href="http://chess960frc.blogspot.com/2019/02/a-stockfish-experiment.html" rel="nofollow noreferrer">this report on blogspot</a>.</p>
 3237: <p>I asked myself the same question a year ago.</p>

<p>I found this interesting page: <a href="http://computerchess.org.uk/ccrl/404FRC/opening_report_by_white_score.html#table_start" rel="noreferrer">http://computerchess.org.uk/ccrl/404FRC/opening_report_by_white_score.html#table_start</a></p>

<p>With statistics for every 960 positions based on 144,300 games played by 123 engines.</p>

<p>Apparently the position that gives the biggest advantage to White is RKNQBBNR with a White score of 63.9%.</p>

<p>Note that on the previous page the standard position has a White score of 56.0%. I once read that the true White score in standard chess is 55.5% for GM games. Since these two numbers are pretty close it would seem that the statistics of the previous page are meaningful and pretty accurate.</p>

<p>Also, someone once told me that if we just inverted Knights and Rooks then White would have a big advantage: NRBQKBRN.
But the previous page actually says that White only scores 47.4% in that position, so maybe he was wrong.</p>

<p>Anyway, I seriously doubt there exists a position where White has an advantage of +0.50 or more. And every single one of the 960 positions are very probably just draws with best play.</p>
