(Quick note: LevelDB is discontinued, so you would want to use RocksDB instead.)
You would need to benchmark them to figure out which one's faster in your application. Speed was not the motivation in creating the LevelDB/RocksDB cache. The requirement was a "maximum size cap" on a cache data, which is not possible with the default filesystem cache. RDB provides this with its "max_size_mb" property, which will make a valiant attempt to avoid going too far past the limit.