Choice of medium is partially governed by how you take care of plants. Busy people who underwater might have happier Oncidiums with sphagnum. Clay pots evaporate water from their surfaces and cool the roots, which is also good for most Oncidiums.
But beware wet sphagnum and hot temperatures (100 F / 38C plus) - they die quickly if that happens.
__________________ May the bridges I've burned light my way.
I think the accordion wrinkles in this photo are from the plant being too dry at the time. Just something to keep in mind. At some point, it was thirsty.
But otherwise, it's a heck of an orchid. Congrats!!