cap heads are the bigger screws heads that take the 2.5mm wrench. I think you might be mixing up "button" and "cap" head. Tony uses all the "cap" head screws he can because of the bigger 2.5mm opening and they are a more durable screw.
How worn down are your Hudy drivers, one of my 2.5's is blown out and will strip screws (the other sizes work because they are not worn down).