Claudia, where did you buy this plant from? I think it would be also advisable to contactthe nursery, send them the picture, and ask for their opinion. Hybrids can have a great variation between seedlings and everytime you make the cross. therefore, you can have plants which are quite different from each other (sometimes to expremes like in Phalaenopsis complex hybrids!). You can have nice examples of hybrids variations in these links:
Phragmipedium Primary Hybrid Photos
Phragmipedium Complex Hybrid Photo Gallery
In the Case of Phrag. Calurum and Phrag. Sedenii, where they actually share the same genes pool, you can have very similar individuals between both crosses.
Phrag. Schroederae tends to have longer petals, as 'gands' said. That's the Phrag. caudatum influence.
Funny thing regarding Phrag. Schroederae (Phrag. caudatum X Phrag. Sedenii)... It has been registered as Phrag. Schroderae at the RHS site
It should actually be Schroederae, as it comes from the german family name Schröder (Schroeder)