best way to do is it lookup

Last time I tested search was significantly faster than lookup. Did that change or why is lookup better than search?

what's the code snippet?

a lookup is less governance than a search thats about the only reason.... it SHOULD be faster since you have the exact data you're after but its NetSuite so could go either way.

the code for nlapiLookupField should tell you that they are probably very similar in performance

function nlapiLookupField(type, id, columns, text) {
  nsapiCheckArgs(
    [type, id, columns],
    ["type", "id", "columns"],
    "nlapiLookupField"
  );
  nsapiCheckType(type, "nlapiLookupField");

  var searchcolumns = new Array();
  if (isArray(columns)) {
    for (var i = 0; i < columns.length; i++) {
      var column = columns[i];
      if (column.toLowerCase() != "recordtype") {
        var name =
          column.indexOf(".") != -1
            ? column.substring(column.indexOf(".") + 1)
            : column;
        var join =
          column.indexOf(".") != -1
            ? column.substring(0, column.indexOf("."))
            : null;
        searchcolumns[searchcolumns.length] = new nlobjSearchColumn(name, join);
      }
    }
  } else if (columns.toLowerCase() != "recordtype") {
    var name =
      columns.indexOf(".") != -1
        ? columns.substring(columns.indexOf(".") + 1)
        : columns;
    var join =
      columns.indexOf(".") != -1
        ? columns.substring(0, columns.indexOf("."))
        : null;
    searchcolumns[0] = new nlobjSearchColumn(name, join);
  }

  var result = nlapiSearchRecord(
    type,
    null,
    new nlobjSearchFilter("internalid", null, "anyof", id),
    searchcolumns
  );
  var results = null;
  if (result != null && result.length > 0) {
    results = new Object();
    if (isArray(columns)) {
      for (var i = 0; i < columns.length; i++) {
        var name =
          columns[i].indexOf(".") != -1
            ? columns[i].substring(columns[i].indexOf(".") + 1)
            : columns[i];
        var join =
          columns[i].indexOf(".") != -1
            ? columns[i].substring(0, columns[i].indexOf("."))
            : null;
        results[columns[i]] =
          name.toLowerCase() == "recordtype"
            ? result[0].getRecordType()
            : text
            ? result[0].getText(name, join)
            : result[0].getValue(name, join);
      }
    } else {
      var name =
        columns.indexOf(".") != -1
          ? columns.substring(columns.indexOf(".") + 1)
          : columns;
      var join =
        columns.indexOf(".") != -1
          ? columns.substring(0, columns.indexOf("."))
          : null;
      results =
        name.toLowerCase() == "recordtype"
          ? result[0].getRecordType()
          : text
          ? result[0].getText(name, join)
          : result[0].getValue(name, join);
    }
  }
  return results;
}

If possible just do the field sourcing.

I just tested again, lookup is slower. I did 40 loops to compare. Lookup is around 15% slower than doing search on average, at least in 1.0

in 1.0, nlapiLookupField uses nlapiSearchRecord internally