Santiago is a really boring city. During the winter you can go skiing in the mountains close to Santiago -1 hour drive up and another down-. However, Santiago doesn't have much to offer to justify the burden.
I've been to Santiago many times already, and it has changed radically during the last 20 years thanks to the economic bonanza of the Chilean economy. Nightlife doesn't exist, seafood and wine is good, but in general there is a limited offer of places to go. Although the Chileans are educated people, the there is no major Museum or cultural attraction in Santiago. There is plenty of new buildings, malls and Hotels, but that's about it. Maybe that is the reason why Chileans pick Buenos Aires as their proffered destination short escapes.
Buenos Aires on the other hand, has it all. Museums, architecture, both contemporary and from all days, parks, nightlife, restaurants, bars, cafes, and of course Argentine girls -bit hysteric though-. Buenos Aires is full of history. From the golden years when Argentina was the 5th richest nation in the world, to the economic collapse. From Peron and Evita presidency to the bloodiest military dictatorship in Latam. From visionary constituents of the country that help the country to have the widest middle class in Latam to the greedy and corrupt President Menem that helped to wipe out a large chunk of the middle class.
I had the chance to live many places across Latam, and there are 2 cities that have no competition whatsoever -at least in Latam-, Rio de Janeiro and Buenos Aires. At least for me, Santiago is way back in the scale. It is great for doing business, shopping. Clean and well organized, Snatiago is the least latin american city in latam. On the other hand, Buenos Aires has the charm of the old days -architecture, parks, streets, buildings-, and the pulse of the modern city.
Do not think twice, go to Baires.