Latin America South prices identically to LAN and restocks just as quickly, so the choice between the two really comes down to ping and to where your duo partner plays. What LAS has going for it is soft ranked MMR — the ladder is less compressed than the European shards, and a smurf that actually is a smurf tends to climb out of the lower brackets faster here than almost anywhere else.
That makes LAS a sensible shard for anyone who wants to see visible progress rather than grind a hundred games for one division. Take an Unranked Smurf with fresh MMR, play the ten normals, and let placements put you where your play says you belong instead of inheriting somebody else's losing streak.