Wonderful article, and very conducive to thought!
I myself greatly prefer bottom-up design for my games and worlds. This is largely due to my personal temperament, and I've seen plenty of really cool top-down worlds (my oldest gaming buddy does his worlds that way, and his campaigns are awesome). But a lot of it depends on what your strengths as a GM are.
I've found over time that I do much better with detailed, intimate settings than I do with sprawling and varied landscapes. One of my favorite campaigns ever took place entirely in a small, isolated valley that was inescapable and focused on the situation of the poor fools who were still trapped inside. There had once been three villages in the valley, but in the wake of a mysterious black rain that swept through the valley a generation or two ago the dead started spontaneously coming back to life and wandering around. The other villages were overrun, leaving just the one still there, teetering on the brink of destruction. I loved it because we ended up delving into extreme depth about everything in that town and that valley--every villager became an important NPC, every building had a clear image and a story by the end of the campaign, and all the little stories and legends of the area wove together. I found that, by restricting my scope, I was actually able to offer more places to explore than a larger world would have offered--every cave and old mine, every ruined mill, every forest thicket and old road, and each of the old towns and all the buildings contained in them. If you have a world with 10 points of interest in it, how much does it actually matter whether they are spread out across the entire world or concentrated in a smaller geographic area?
It's like freeway travel vs backroad travel. If you drive on the freeway you can travel very fast and you will get where you want to go very quickly and very efficiently, but everything looks pretty much the same, and you run across the same signs and gas stations and restaurants the entire way. Traveling on the backroads means you can't travel as far, but you will see a lot more. You'll see all the little rivers and creeks, the farm fields and houses and the different barn styles as you travel across the country. You see unique houses with unique things in the yard--some places will have neat lawns and beautiful flowers, others will have lots of toys, others will have rusty junk. You come across small businesses that you will only find in this one little town, and weird people who will say things you haven't ever heard before. When traveling through cities you will see each neighborhood, noticing the differences in architecture and how some are newer than others. You will go through different ethnic districts, seeing signs change from English to Russian to Chinese to Arabic and others. You'll hear street musicians playing, you'll see block parties and neighborhood festivals celebrating some local celebrity that people elsewhere don't even know about. Each has advantages and disadvantages, and each will give your game a different feel.