Thanks for the answer and i agree with you on everything you say in that its very unlikely humans will ever reach a common consensus on outreaching from our own planet in economic terms, when i simplified it to 'warming up' andcooling down' I understand that a lot more processes would have to ocur afterwards to make a planet inhabitable but what i really meant by that second part was whether we would find it easier to add to the Martian atmosphere (to start the proces of terraforming by increasing the global temperature) or would we find it easier to remove some of Venus's atmosphere to lessen the greenhouse effect and therefore slowly cool down the planet to more favourable temperatures? (which makes me wonder whether if one day we had the resources we could merely transplant some of Venus's grenhouse gases into the Martian atmosphere?)

Your points are reasonable, but the theme is complex. I have written a fair amount about such themes, and we might be reduced to using another medium, but let's see what we can do immediately, before I know how deeply you wish to explore the subject.

Firstly, the actual twilight zone would be uncomfortable because it would coincide largely with probably the most concentrated constant velocity convection wind in the solar system. It would be the wind-power engineer's dream. 365.25 days per Earth year of 100% power, probably enough for the planet's entire residential energy supplies, and then a lot more.

But then, "twilight" is a relative term. the lower the sun in the sky, the lower the insolation. I reckon that the cooler 50% of the planet's surface would receive roughly the intensity of sunlight that we get on earth, and before you sneer at 25% of the planet's surface, remember that that is how much of the Earth's surface we use.

The central area with the sun generally just about overhead, would receive about twice our solar intensity, which might be a little uncomfortable for exposed people, but should be great for industrial sites. Sure, staff would not go and sit outside in parks during lunch hours, but aircon would be no trouble, given the cheapness of solar power.

Reticulation? What reticulation? Just put up a solar power brolly or two!

And let's see you try that on Mars!!!  ;-)

As for the resultant temperatures in the open, sorry, I cannot give you any confident details. It might be that we never live in open-air Venusian ranches, unless we manage to breed some very special plant life, but it also might well be possible. That is a quantitative question, not a qualitatiative one. The compositioon of the atmosphere might well be a problem, with too much CO2, or, even too little CO2.  We certainly can make any of several schemes work, but whether the most successful ones would be highly, or alternatively, hardly technological, I canot yet say.

All I can say is that it is possible at a profit, speaking species-wise.

And again, let's see you try to claim that about Mars with any justification!!!  ;-)

Mercury is a slightly different case, but the fundamental argument about usable power remains in force.