Fortunately, they both need the same type of soil.  They should be planted in well-draining and well-aerated soil, such as Happy Frog potting soil, an Aroid soil mix, or a homemade mix containing 50% perlite and 50% coco coir. The difference in their soil requirements will come with pH levels.  Philodendrons prefer slightly acidic soil that ranges between 5.0 and 6.0.  Pothos plants prefer soil that ranges between 6.1 and 6.5.  It is very easy to test soil pH levels with a Soil pH Meter and adjust the levels up and down by adding different organic materials.