1) Points. More points are always better than less points
2) Sente and threats. Imagine there is some small ko left on the board. If you get the most points you can, you can improve your result by ending in sente and having as many ko threats as possible to get to the ko first.
(;AW[qb]AW[pb]AW[pc]AW[rc]AW[rd]AW[qd]AB[pd]AB[od]AB[oc]AB[nb]AW[oa]AW[pa]AB[ob]AB[na]AB[re]AB[qe]AB[rf]AB[pf]AB[of]AB[qg]AB[pg]AW[rh]AW[qh]AW[si]AB[ng]AB[nf]AB[oe]AW[pi]AW[oi]AW[ni]C[Black wants to play the best endgame.]AB[ph]AW[nh]AB[rg]AB[sg]AB[se]AW[sh]AW[qj]AP[goproblems]
(;B[oh];W[sc]C[Black has no threat now!])
(;B[sc]
(;W[sb]C[CHOICE];B[sd];W[oh]C[Well done, you made one ko threat and kept sente!RIGHT])
(;W[sd];B[rb];W[sb];B[ra]C[White cannot play this way.RIGHT]))
(;B[sd];W[sc]C[Your marked move was just zero points making two threats. White could not play at T16 anyway.]TR[sd])
(;B[rb];W[ra];B[sc];W[sb];B[sd];W[oh]C[You wasted one threat.]))