user4399: From Lichess page 'Chess rating systems':
Question:

Which rating system is best?

Answer:

The purpose of rating systems is to predict the outcome of games. Therefore, they can be objectively better or worse, according to their ability to make such predictions. Glicko 1 makes better predictions than Elo, and Glicko 2 makes better predictions than Glicko 1

My question: Is 'predict the outcome of games' the same thing as 'reduce the number of upsets' ?
Upset here is simply lower rating defeating (or drawing against?) higher rating. Thus, assuming all ratings are integer valued and no 2 players of equal rating play against each other, what I understand is that
'1800 is more likely (or at least as likely) to beat a 1700 if the ratings are glicko 2 as compared to glicko 1'
if and only if
'Glicko 2 makes better predictions than Glicko 1'
Is there anything I misunderstood?

user26072: Basically correct. (Note that these rating systems don't natively deal with draws, only with binary wins/losses. Draws are incorporated by summarizing results as point-score = wins + 0.5 * draws.)

4399: <p>From <a href="https://lichess.org/page/rating-systems" rel="nofollow noreferrer">Lichess page 'Chess rating systems'</a>:</p>
<p>Question:</p>
<blockquote>
<p>Which rating system is best?</p>
</blockquote>
<p>Answer:</p>
<blockquote>
<p>The purpose of rating systems is to predict the outcome of games. Therefore, they can be objectively better or worse, according to their ability to make such predictions. Glicko 1 makes better predictions than Elo, and Glicko 2 makes better predictions than Glicko 1</p>
</blockquote>
<p>My question: <strong>Is 'predict the outcome of games' the same thing as 'reduce the number of upsets' ?</strong></p>
<p>Upset here is simply lower rating defeating (or drawing against?) higher rating. Thus, assuming all ratings are integer valued and no 2 players of equal rating play against each other, what I understand is that</p>
<p>'1800 is more likely (or at least as likely) to beat a 1700 if the ratings are glicko 2 as compared to glicko 1'</p>
<p>if and only if</p>
<p>'Glicko 2 makes better predictions than Glicko 1'</p>
<p><strong>Is there anything I misunderstood?</strong></p>
 26072: <p>Basically correct. (Note that these rating systems don't natively deal with draws, only with binary wins/losses. Draws are incorporated by summarizing results as point-score = wins + 0.5 * draws.)</p>
