See, this is big debate because both the colleges are world class and its hard to differentiate between them.So, you will have to decide.
Doon business school is considered better than UPES in terms of ROI and course fees, academics and faculty members are also good.
But, also on the other hand UPES is better in terms of placements, curriculum and infrastructure.
So, there is a cut throat competition between both these college there is no strong reason to consider one of them as second best.
I hope this helps.