The seki-in-gote option is shown here.
Even though Black has no territory now, there is still the option of playing at a. If the outside is White's territory, this would be 5 miai-points in a typical endgame situation. Black may even play at b to help an invasion.
The hemming-in-in-sente option is shown here.
Compared to the seki-solution Black has 3 point territory more. On the other hand Black loses the option at a. Whites also captures 1/2 stone.
Black lives by capturing three to make an eye.