Your standard type of High Flow Cat is usually a ceramic internal type, where the dearer Catco, X-Force and BPM 'Metal' or 'Metallic' Cats use a stainless biscuit core and flow a lot higher.
There is NOTHING wrong with X-Force Cats as above, dependent of course on the vehicle and its level of modification.
For the price, I don't think you can go wrong, and I have used one on my old GTS-T and had no problems at all with a significant performance gain.