What nobody tells you about Ghaziabad's 'full power backup'

The full power backup claims by builders in Ghaziabad always seem too good to be true. I'm fed up of renting, finally looking to buy, maybe Mass Build Well Livin' Life. But for an investment property, how crucial is proper full flat backup? Does just common area backup affect tenant attraction or resale value much? Or is it mostly a marketing gimmick?