Which will be a better career for ECE engineers, IBPS SO or PSU via the GATE?

Some of my friends work in both the departments and based on their experience, I can answer this.

If you look at the position of an IBPS SO, it's that of a specialist officer. You'd technically be a network administrator of all of the intra networks of the bank. You'd be a database administrator/database manager who would have the entire intra network of that particular bank under your supervision. 

Now if you look at the PSU job, you'd be someone who would be responsible for sustaining the technicalities concerning PSU.

Your enquiry on which one is better entirely is up to you and where your interest lies. While some might opt for GATE which concerns their core subjects entirely, others simply might find their area of interest in networking. So, decide for yourself and choose what suits you and not the rest.