Please help explain the best play here. Thank you!

Life is much harder for white playing from the ace point vs a five prime than it from the deuce point vs a four prime. Getting hit on the ace is not very bad as we are only up against a 3 point board and have a threat to hit the checker on the 16.

So getting hit is not that bad, but more importantly, we win a ton more gammons and backgammons when we close the whole board up ASAP. This is much easier playing 8/2* 3/2 than it is playing 8/2* /1.

Low risks and large rewards are rarely bad

8/2* 3/2

^^ +1

After making the 2pt, Black’s numbers are well diversified. 6 won’t play (unless accompanied by the 2 or 3 that releases Black’s rear checker). 5 and 4 cover (or hit) on the 1pt. Finally, 3 and 2 move the rear checker into escape position. Only 1s are not constructive, but neither are they destructive.

Contrast this with the unhappy duplication that occurs when Black makes the 1pt. As above, 6 plays (or does not play) quite nicely, but 5 is deadly, killing a checker, while 3 and 2 are both duplicated. Only 4 and 1 are available to make the unslotted 2pt.

As others have already noted, should White enter, the five-point prime is a far more substantial block than the four-prime.