which method should use to concatenate two pdf files

I saw there are two different way:
1. use Aspose.Pdf.Facades.PdfFileEditor
pdfEditor.Concatenate(inputFiles, outputFile);

2. use Aspose.Pdf.Document
document1.Pages.Add(document2.Pages);
document.Save(outputFile);

Could you tell what's the different
And please also tell me which one is recommended and why?

Thanks


Wei