How would you play:-

Jxxxx

AK8x

for 5 tricks (easy) and

for 4 tricks (Dave's not sure he would get this one at the table!)?

For 5 tricks, you play the AK, hoping that the queen is singleton or doubleton.

For 4 tricks, you lead towards the J.  If LHO has all 4, then you only lose the Queen.  If RHO has all 4, you still have the finesse position of AK8 in hand.

Correct for 5 tricks - 53% chance.

For 4 tricks the stated best play is - 'Lead low to the eight in case West (LHO) is void'. This is quoted as a 100% chance.

They usually quote equal alternatives but as leading to the jack also appears to be 100% they don't appear to have done so in this instance. Are we missing anything?

How would you play at pairs?

Leading to the 8 has the advantage of a singleton Q in the East hand, thus making 5 tricks; playing to the J will only ever make 4.

Thanks to Simon for pointing that advantage out. Given this, Dave would have expected both plays to be listed (as they both are 100% for 4 tricks) with (best) against the lead to the 8.

At MPs I would cash suit from the top (unless there was a clear indication that West was void) and make as many tricks as all the other pairs. If it was a situation where everyone is likely to be in, say, 3NT and we have bid to 4 of a major with both contracts making the same number of tricks (10, 11 or 9) when played as above, I would play for West to be void and follow the 100% line for 4 tricks, thus turning our bottom into a top, when we make 10 tricks and other pairs only 9.

Dave would also play the suit from the top and finally towards the jack at pairs but he's not sure he would have sufficient confidence in the rest of the room's choice of contract very often to change his play as Simon suggests! Of course he is right in principle.