Have you ever heard of game engines? IL-2 has a completely different game-engine featuring a completely different structure of development. Meanwhile, if you look at Aces High, it could be a completely different story.
For example, One town was built in a, "square" format. Instead of simply placing structures or roads wherever it pleased them, they placed it in precise locations to ensure conservation of space. Another town of relative size decided to build wherever they felt a building would fit and simply, "built on the fly." Well, eventually both towns had a need for a new grand hotel featuring 35 stories of suites. No problem for the, "square" town. They simply demolished a neighborhood and started building. However, for the other town there were problems. Their structures were strewn all over the place to the point that they had no room to place the structure. Of course they could demolish some buildings, but it wouldn't allow the new hotel good access to main roads or government buildings. So the town had to demolish even more buildings and even had to relocate some roads before making a decent amount of room for the hotel.
While this may not be the situation with HTC, it does give you a little insight to programming in general. It's the very same hotel (feature), but one city (game engine) was better prepared to implement something new than the other city. Thus it reduced the amount of time to construct the hotel (feature) for one city while it caused nightmares for the other.