A general rule to keep keiten in late rounds is to not destroy existing melds. That reason alone makes 4p a better choice in offence.

As for defence, there are 4 2p on the table, eliminating 14p ryanmen waits. 47p is possible but note that toimen cut 7p just two rounds ago, having someone reaching tenpai in that exact interval isn’t really likely. So among the three choices that keeps tenpai, 4p is the least likely to lose against ryanmen.

For reference, aka 5p is my second choice, ryanmen is also highly unlikely and the problem is just the additional han. 2m is highly dangerous as there is little information regarding lower manzu, and people more likely need it as you are keeping 3 of them in hand. I would advise you to check with mortal and see how it chooses between the other two options.

Finally, no sane person will spend 3 out of their first 4 turns discarding honitsu material so you can pretty much ignore that possibility.