no such thing as a universal standard, but some of them formats are fairly popular. it depends what you expect from the format - if you're looking for something that can serve both an educational and a practical purpose, i'd say go with simpler formats initially, even if they did not have all features you envision as needed. if you want to dive right into the deeper end of the pool - go for collada (v1.4) meshes - that standard has everything and the kitchen sink when it comes to 3d assets exchange, and it is an open standard too.