I would choose Venus. The depth of the gravity well is less important when the colonists are being lowered into it from above rather than thrown out from the bottom. If you need something in orbit, you don't drop it down to the planet in the first place.

But as things are, the relative effort to terraform Venus, compared with Mars, is absolutely colossal. It essentially requires a full-blown robotic asteroid mining industry, wherein olivine asteroids are diverted directly to Venus, and magnesium and calcium are mined, sent to Jupiter to produce saturated hydrides, and those sent on to Venus. It will take 1000 years, minimum.

Mars can get realistic results within 200 years, just by diverting water-ice comets and managing temperature.