I would always be inclined to go for Bosch, although there are NGK coil packs available, and given NGK's quality / reliability with standard spark plugs, you would think their coil packs should be of the same standard.....but if there was a Bosch available, I think I would still go for the Bosch.
Whilst on the topic of Bosch coil packs, I have seen the 246 side advertised for a Vectra 3.2, but with the part no 0221 503 473, whereas the Omega is 0221 503 027.
The only visible difference is that the sealing rubber around the coil pack listed for the Vectra is light grey whereas the Omega is black (they both have the grey plug).
On the Bosch website, the 135 pack for the Vectra and Omega is listed as the same pack, whereas the 246 has the two different part numbers for the two vehicles.
Anyone any knowledge of the difference? I know someone who has put the above Vectra pack in an Omega and it appears to be running ok.
I wondered if the difference was an improved sealing rubber, as we all know the issues with possible water ingress (when fitted in an Omega)?