Ehisey covered most of the high points rather well. TLX is a new format that supersedes the older static formats in terms of how we create content, and SwiftScenics was designed to complement TLX. As such, if you're already happy with the older format and you don't see any appeal in the new formats, there's nothing wrong with you sticking with the old format. The old stuff's still good and does what it was originally intended to do very well. In practical terms, the only thing that changed is we're not developing content using the old formats anymore.
As for the pricing/content load issue, selling them individually was something I encouraged Matt and Denny to do. One of the reasons Denny wanted to give me a job here last year was because of my insights and experience with the industry in general, and I specialized in microreleases when I was still running a business of my own. Over most of the decade, I've tried pretty much every permutation of selling things that came in a lot of variations, and the one that works the best in my experience is to break things down individually so customers can choose what they want.
The biggest reason is to embrace agility and flexibility. If you start with 1 set = 1 building, you have the ability to flexibly adapt to customer tastes one building at a time, and you don't constantly end up in a situation where you have to scrape the casserole pan to come up with an additional X variants to form a salable unit.
The second biggest reason is balancing workload with customer choice. Selling things in large bundles forces you to walk a really fine line as a designer. If you put in too many variations and charge too little, you end up spending too much time on the project and it takes that much longer to sell enough copies to pay for itself and put food on the table. If you put too much into a set and charge accordingly, it fosters a perception that people are paying for extra stuff they don't want or need, and they may start complaining that they just want 1 or 2 parts of the whole sold separately. If you bust everything loose into smaller units, it gives people the opportunity to choose only the things they like without having to pay for stuff that they don't want.
The third reason is more of a benefit for the company itself: to establish a baseline value threshold to work from. If a single building is known to be worth, say, $3.50 or whatever, then it's a lot more likely that any one given designer will be comfortable with the idea of doing a new SwiftScenics structure, and it gives us a nice introductory platform for new designers to cut their teeth upon. Before this, getting new designers onboard was very difficult because their debut product essentially had to be a huge $18 set (by old pricing), and that was an intimidating threshold. That's no way to grow a company--we need to be able to give the probies something confidence-building that they can complete without losing the will to live.
I hope I managed to clarify things a bit.