More equipment is involved in a land landing. That's more that can fail. you also have to consider where they're going to have an abort landing. The Soviet's

More equipment is involved in a land landing. That's more that can fail. you also have to consider where they're going to have an abort landing. The Soviet's launch locations weren't exactly surrounded by oceans. I'm sure landing in the Caspian Sea was undesirable to them for other reasons.