One of the great things about our huge database of cribbage games is that we can identify hands that are frequently misplayed. Today we're going to give a high level overview of a few of those hands. Keep in mind that these results aren't our opinions  they're the actual results across a sample of millions of cribbage hands. Some of these results are just as surprising to us as they are to you.
A4XX
About 4.8% of pone (nondealer) hands will hold an ace, a 4, and two 10s/face cards. (From now on we'll use "X" as a shorthand for "a 10 or a face card"). Most players lead the 4 from this hand, but around 7% lead the ace. The players that lead the ace, on average, have a 0.55 point pegging advantage: they peg 0.18 points more, and their opponents peg 0.37 points fewer.Why is the ace a better lead? There are pros and cons to either lead, but our data shows that by far the biggest factor is that dealers are less likely to pair an initial ace. Of the tens of thousands of A4XX hands that we've analyzed we've seen that the dealer pairs a lead 4 at 19.93% of the time, but only pairs a lead ace 12.84% of the time. An interesting and common case is when both players have A4XX hands. Here's how the pegging plays out in that scenario when dealer is willing to pair a 4 but not an ace:
Pone leads a 4
Pone

Dealer

Points

4
 
4
 +2 for dealer (pair for 2)  
X
 
X
 
A
 
A
 +3 for dealer (pair for 2 and a go)  
—
 
X
 
X
 +1 for dealer (go) 
Pone leads an Ace
Pone

Dealer

Points

A
 
X
 
4
 +2 for pone (15 for 2)  
4
 +2 for dealer (pair for 2)  
X
 
A
 +1 for dealer (go)  
—
 
X
 
X
 +1 for dealer (go) 
Leading the 4 gives dealer 6 points to pone's 0 for a net disadvantage of 6. Leading the ace gives dealer 5 points to pone's 1 for a net disadvantage of 4. Executive summary: lead the ace from A4XX.
A789
Most players lead the 8, but leading the ace gives a 0.78 point advantage (pone pegs 0.38 points more, and dealer pegs 0.40 points fewer). The data shows dealers making a couple mistakes when pone leads the ace: Dealers holding 5XXX see the ace and expect pone to have a 4. Dealer plays her 5 to avoid giving pone a a 152. Pone plays a 9 on dealer's 5 and pegs 15 for 2 points.
 Dealers holding middle cards (6s through 9s) end up trading runs back and forth with pone, and usually lose in this situation
Executive summary: lead the ace.
AA59, and A689
At the risk of seeming predictable, we're going to suggest leading the ace for these two hands. AA59 is one of the few hands that most players are playing properly: 50.3% of Cribbage Pro players lead the ace from this hand.Leading the ace from AA59 averages a 0.50 point advantage over leading the 9. Leading the ace from A689 averages a 0.57 point advantage over the 8 (the most popular lead, and the second best choice).
Executive summary: lead the ace.
5567
The last hand we'll look at today is 5567. Most players correctly lead the 7, but about a third lead the 6. Leading the 7 gives a 0.57 point advantage over the 6.The big story here is that pone comes out better if dealer plays an 8 on pone's 7 than if dealer plays a 9 on pone's 6. When dealer plays an 8 on pone's 7, dealer averages 7.59 points of pegging to pone's 3.68 (for a net 3.91 loss for pone). When dealer plays a 9 on pone's six, dealer averages 5.99 pegs to pone's 0.88 (net 5.11 point loss for pone).