- Size. N scale, in my opinion, is the perfect scale for apartments and mainline operations. Yes, it's small, but the engines run well and everything is just big enough that, provided there's no sight or hand problems, it's possible to build high quality and fun layouts. The 1:160 scale also means that there can be a great focus on scenery and prototype length trains. A 100 car train in HO scale is difficult, but it's possible on a moderate layout in N scale.
- DCC and Sound. About 10 years ago, it was rare to see N scale with DCC installed, let alone DCC and Sound! But within the last decade, that has changed. Now N scale locos are not just offered with knuckle couplers as standard, but also with installed DCC. A few, such as the Intermountain SD40-2's, have sound installed as well as DCC. It's now possible to run an N scale layout just as HO modelers do.
- Modular groups. N scale has several modular standards. NTrak, Ttrak, NMRA, and Freemo are just some of the standards.
- Small radius. In N scale, a 2 foot wide shelf is enough to make a complete turn with the track. It doesn't look pretty, but 9.75" radius curves get the job done. While the standard HO beginner layout is 4x8, requiring an entire room, for N scale the size is a much more manageable 2x4. All a 2x4 layout requires is the corner of a room, or one end of a table.
- Space to grow. While a 10x10 room is modest by HO scale standards, 10x10 is a sprawling pasture for your N scale equipment! At 32 feet per scale mile, a 10x10 room can host a couple miles of track in N scale. For HO scale, you'd be lucky to get more than 3/4ths of a mile.
- Large radius. Let's say you've got space, enough to do a decent railroad in HO scale. You could go with HO scale and build a railroad that looks okay in the corners, but large equipment will be difficult to run. In N scale, having an 18 or 22 inch radius is more than enough for all but the largest equipment. And if you are running 50 foot cars, they'll look very good rolling on a broad curve. Heck, the minimum prototypical radius in N scale is 6 foot. If you have a 12x20 room, half a basement, you could theoretically model something to scale.
- Operations. David Popp has been a great inspiration to me through the last 12 years or so. His now famous New Haven railroad was built for operations, and it is in N scale. Also, just to note, David wears glasses, hence no 20/20 vision for him. And yet he's been able to build an run a fantastic railroad right up until selling it a couple years ago. I've personally seen that it is possible to read car numbers for waybills. Yard tracks may have to be a bit more separated, but it's possible to switch out an entire yard without incuring problems.
- Detail. N scale detail in high end models now rivals that of HO scale. Soon it could be even better. Not to mention, you see less detail in N scale, so at a certain point the models will "look right" even if they aren't the sharpest or most crisp for details.
- 3D printing. In other scales, you can print parts for models. In N scale, you can print the model! The only other scale I've noticed that can do that is HO, but only with narrow gauge models. Standard gauge trains are still just a bit too big. But in N scale, equipment and small structures can be printed in one piece, making the whole process easier. Some will decry that 3D printing will make scratchbuilding obsolete. To that, I say that few people have attempted all-out scratchbuilding in N scale, so it is of no loss to the small scale modeler to be able to print almost anything as one piece, or as big pieces. Less time on the work bench is more time running trains.
- Finally (just to round it off at 10) there's the future. Families are getting smaller, income is tighter, and we could very well be living in a more compact world in the future with population growth. US modelers will be lucky because most of us still have more space than the rest of the world (except, apparently, Australia, which has a larger average home size). HO scale will still be the majority, probably. O scale and S scale have been having smaller followings in recent decades while other scales have grown. Those with a yard will still do G scale. But for the townhome, the apartment, the condo, the tiny house, the RV, the people who are on the go or living small, N scale has now become the best option to enjoy the hobby without eating up real estate. N scale has all the same advantages as HO, but in a smaller package. The smaller space requirements means that N scale will go places, figuratively and literally.
Of course, time will tell how all this pans out. But at this moment, I feel that N scale is making a strong case for itself. Perhaps Z scale will one day be considered the smallest practical train, and HO will be replaced by N scale in popularity. Perhaps not. But one thing is for sure, N scale is here to stay and has a growing following that attracts not just the old folks, but also the newer (younger) blood. Better eyes and hands along with a small space and moderate price means that people who are in their 20's and 30's will find N scale attractive to their wants and needs.
As for me, I think N scale is my future. I still want to try HOn3 and On30 narrow gauges (which can be built to similar space requirements) but when I think of mainline and branchline operations, N scale is now more appealing than HO.
My two cents.