Hi Kumar,
I'm using HDFC account since 2013 and SCB since 2017; here's my 2cents on the overall experience.
Branch Experience:
SCB wins over HDFC.
HDFC feels like any other Govt/Private Bank with usual queues and wait times, but SCB always offers better customer experience; top-notch service quality and premium feels.
However the branch presence of SCB is quite limited and mostly in Metros, HDFC has branches and every nook-and-corner.
Online Banking Experience:
Again I feel SCB has an upper hand due to a very institutive and user-friendly online banking portal; the HDFC portal seems quite old-school and dull.
But in both, you can get most of your work done online and hardly have to visit the branch.
Relationship Management and Wealth:
SCB has Priority Banking which requires atleast 30L of Funds under-management viz-a-viz HDFC Imperia which requires just 10L
However SCB has a dedicated team and wider product offerings, especially in terms of managing investments.
Disclosure:
I was previously working with Standard Chartered and may have a bias towards the bank. But said that, from a customers point of view too, I always loved the experience which SCB offered over HDFC.
And in banking world, where almost all banks offers the same products and rates; its the Experience which is a key differentiator.