Well, regarding the trekking routes from Tengboche to Lobuche via Dingbuche and Pheriche; there are different descriptions for every trekking agency and guide. But according to my experience since 2001 as a trekking porter, Guide and now, I would like to recommend you Tengboche to Lobuche via Dingbuche while going up, Dingbuche is a much bigger place than Pheriche and the most beautiful mountain scenery and it is much more wormer than Pheriche. To get its most popular viewpoint “Nangkhartasang Peak 5,615m” from Dingbuche are also shorter access. But when coming if you like to come through the Pheriche you can come or stay overnight as well. Other things why people would like to stay in Pheriche; there is a hospital conducted by the Himalayan Rescue Association (HRA), where every day about one to 3 PM they have a conference about height altitude sickness.