Late to the party, as usual ...
IIRC I already had a discussion with PovG about the Venus vs Mars thing, and I'm still firmly convinced that Mars would be easier to live on and "possibly" terraform than Venus. That being said, I don't believe, as others said as well, that we should be really thinking about terraforming either of the two, both are really unsuited for a similar process, IMO.
I mean, terraforming (which I like to remember it's just a theoretical process, almost nothing of it has been tested yet) is an incredibly complex process, which can take thousands and thousands of years and that could be subject to sudden, unpredictable events, that will kill all that has been done before. In general I would say that the very idea of terraforming is very
impractical, to use a mild term.
If we'll ever try something like that, it will be only on a planet/moon which is already very close to Earth's native conditions, in particular for what regards non-toxicity/non-corrosiveness of the atmosphere, the presence of a magnetosphere and an acceptable gravity/pressure and temp at the ground. With a non aggressive atmosphere, the protection of a magnetosphere and "regular" gravity/pressure/temperature, even with the actual technologies we could be able to set up colonies for an indefinite length of time; once the colonies are settled, then the generations long process of "making this rock more similar to Earth", could start. I don't see in any way how it would be logic, or even possible, to terraform a celestial body where you are not already living (the process of improving our own living environment is innate to the humankind, well in most of the cases, at the least
), therefore if said body doesn't have the minimum conditions for the life as we know it to survive for generations, there's no chance that any terraformation would take place. Not Venus neither Mars present those conditions, nor any other body in the Solar System as far as I know.