I think if you ask most of the Stage 2+ lads on here, you will find they are running an OEM valve mate
The original valve was supposedly prone to failure, but it was more common on the K03 cars where the valve is located at the turbo side of the engine, and the Diaphragm would split. As the Cupra has a relocated valve, it was not really an issue.
Regardless, VAG released a new revision valve which replaced the diaphragm for a spring which effectively removes any likely weakness. This costs under £40 and is very easy to change over.
In short, an aftermarket DV is not worth the money it costs over the OEM item and it will be one of the first things a stealer would see when under the bonnet.