My slaves tried both and most of them find holy trainer in general is much more comfortable and ergonomic than CB6000 cages on the precondition of both devices fit them well. I recommend holy trainer V3 & V4 over CB6000 for any chastity beginners if you are looking to get a ball trap chastity device.
However, both ball trap chastity cages are not suitable for the long term. If you want long-term comfort and security, you must get a chastity belt, preferably a breathable chastity belt in custom size.