Staying in orbit means risk of catastrophic failure on puncture and doesn't provide access to the heat of lower layers of Venus atmosphere that can be used as energy source or carbon source. You also have to think about heat management - big colony means gigantic radiators. And most importantly no gravity and no magnetic shield - these make Venus imho better colonization target than Mars.

On Venus, a puncture doesn't immediately destroy anything - because of equal pressure on each sides of the balloon wall. You have more than enough time to put on a protective coat and fix it.

And building more living space is much easier + you could source the material (carbon) on site.