Is it better to install a replacement window from the outside in or inside out?

From the outside,then the opening can be sealed from wind and rain.I've never installed a window from the inside,in my 30 yrs of house building.

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Vinyl replacement Windows are safer to install if you stand inside the building when you're putting the window unit into the hole. Once they're in place you can do all your sealing either from the inside or from the outside--on a double-hung replacement unit, you can remove both sashes and do the sealing easily and effectively. A new construction window, like a homebuilder would install in a new house, MUST be installed from the outside. Replacement Windows don't have that problem.