With technology products, and especially mature categories that mostly see incremental upgrades, the time to buy is when actual shifts, or changes occur that serve as demarcation points. Those also serve as cutoff points when internal decisions are made as to what hardware is going to receive continued support going forward. Especially for Apple. You want to buy when their products make discernible steps…like Touch ID, then Face ID, OLED, and so on, and hopefully land on the "right" side of those lines that will become clearer only as time passes.
The 16/16 Pro has at least two of these, compared to the 14 Pro.
Apple Intelligence. It, and general AI's utility still have to be proven, but what is certain is that only hardware introduced this year will support it. And to support it requires a capable processor and sufficient memory, both of which only the 16/16 Pro possess. The necessary requirements have made the former a beefier model than it might have been, if not for the push for such a feature, due to its potential importance going forward.
Larger camera sensor and periscope lens (Pro). Bench racing doesn't tell the whole story, especially with cameras (recall the megapixel race), but the 16s have better hardware. The potential issue here is that smartphone cameras rely heavily on processing to help overcome the limitations of their camera hardware, and the newer models have been criticized for looking too processed. But, the better hardware can capture more raw data, and be processed manually.
USB-C. It seems like an easy thing to live without for the time being, but it is the modern and versatile standard, and the only standard going forward. Lighting is a legacy standard that will fade, with no reason to buy into it, or an Intel-based Mac.
In the end, the line between pre-AI, and post-AI, is one that shouldn't be ignored. How much practical utility the features will have will depend on the user, and how well they end up working, but at least internally, the thinking and decision making is going to be heavily influenced by that line.
The newer hardware is just at the beginning of its support cycle, and the hardware upgrades it has also make it more likely that it will be supported for a longer period, and not reach the support EOL point sooner. In short, the old "buy the best you can afford" mantra, especially for those who follow a long term ownership cycle.
As others have pointed out, the 16 might be a good compromise, lacking only some flashier features that many might not find essential.
Personally, I have an XS that still does what I need it to do, and decent battery capacity; I don't play carrier games so it was fully out of pocket. Touch ID never worked well for me, but Face ID has been smoother and better than I ever hoped for. The X represented a big shift, and the XS a more polished version. It shipped with iOS 12, and if 18 ends up being the last supported version, will have had six major OS updates.
I'd buy a 16 Pro if it broke, or my hand was forced today. But I can afford to hold out for the 17, and the second generation of the hardware that Apple deems necessary in an AI future, and hope that a similar ownership cycle repeats itself.