This election is unprecedented in that not only do we get to compare the promises of the two leading candidates, but we can look at what they've actually done. Something that's usually hard to pin down is a candidate's vision, but both Ken (2004 and revised 2008) and Boris (2011; largely the work of the late Simon Milton) produced mammoth London Plans during their time in office. They act as the guiding strategy for development to 2026 / 2031 and give us an insight into what these men think London should be.
What's immediately noticeable is how similar they are. And of course they would be: despite all the candidates' catfighting, there are few people who can argue with social inclusiveness, sustainable development and a shift to a low carbon economy, regeneration in areas that need it and generally making London a nicer place to be – or, in Boris's plan, "a city that delights the senses".
Both set additional housing targets at slightly less than studies suggest the city needs (btw, if you want to know how much space London has decreed you need in a new build, check out p87 of the 2011 Plan: two people in a one bedroom flat? 50 sq m) and promote mixed, balanced communities.
The differences? Ken's target of 50% affordable housing per development becomes the "maximum reasonable amount". Ken supports Heathrow expansion only if the effect on air quality and noise can be sorted out; Boris rules expansion out completely (why, hello, yonder Estuary airport). Boris's plan makes a point of flagging up strategies for Outer London. The main differences seem to be those of omission. Boris's introduction says he "avoids setting unnecessary targets where they distract attention from practical action" and the 2011 plan is certainly shorter, with notable removals including renewable energy targets and dedicated development plans for specific London regions.
Of course we should remember that plans are all very well, but it's what you do with them that counts...