Wax begonias bloom more and more, more and more joyfully, leaving you no choice but to love them

Wax begonias have always been the supporting act, set off to one side as a foil for photos of the other flowers. For several months now, they have bloomed more and more, more and more joyfully, while the flowers beside them have withered pot after pot, yet these two have stayed the whole time, making their owner see them in a new light and love them whether they wanted to or not -- and remember, they have been crammed the whole time in little pots only a dozen or so cm across!
It is worth mentioning that I tried growing single-petaled wax begonias in different media, with cuttings taken at the same time, potted up at the same time and planted out at the same time: one pot in garden soil, one pot in discarded imported peat moss that had been used for gesneriads. The difference was obvious -- the one in peat moss was far stronger!