Thanks for the link to your article, which rather neatly summarises the outcome of our last marathon debate on this topic, back in June. Since then I have done a bit more testing, and I find that for the very, very most picky results when using an Epson printer -
* Always upres to 720 ppi
* And I can see a difference in result depending on the starting resolution. For best results I re-size the image to a multiple of 60, rather than a random figure, thus - 180, 240, 300, 360 (of course), 420, 480, 540, 600, 660. So if my image native res was 454 I would re-size it to 480 (smaller) or 420 (bigger). Then up-res it in LR to 720 ppi on its way to the printer.