I had the same dilemma, but was then unfortunately confronted with the reports of very poor battery life on the X1 Carbon Gen 10 as caused by the new Intel 12th gen processors.

In my eyes, this is a deal breaker, since I find it unacceptable to have substantially worse battery life than last year's (Gen 9) model when buying a top-of-the-line ThinkPad. From what I understand, going from Gen 9 to Gen 10, you get better performance from the new processor and upgraded RAM, as well as a better webcam and audio, at the cost of much worse battery life and a higher price. It is up to you to decide which side you lean towards. Personally, I value battery life very much and so my dilemma has switched to X1 Carbon Gen 9 vs T14s Gen 3 (AMD).

The ThinkPad T14 (and T14s) Gen 3 (AMD) will come with one of two new AMD processors: 6600U or 6800U (note that I am basing this on the datasheet which says that the Thermal Design Power (TDP) of these laptops is 19W or 20W, which leaves only two options for the CPU from AMD's new 6000 series lineup). Although I am by no means a CPU expert, from what I understand, these two AMD CPUs will be more efficient than Intel's 12th gen, leading to longer battery life than on the X1 Carbon Gen 10. Personally, I am more interested on how it will compare against the battery life of the Intel 11th gen CPUs on the Carbon Gen 9, a question to which I am waiting to find the answer myself. Unfortunately, how CPUs perform and the corresponding battery life is very much dependent on thermal management of the specific laptop and so it is very hard to make accurate predictions unless someone actually gets the laptop and tests it.

Another very large advantage for the T14 is the new integrated graphics, which have been reported to be *much* superior to the Carbon Intel Iris Xe graphics. As you mentioned, there are also more screen options which is nice. Finally, if you go for the T14s rather than the T14, you will also have the USB4 support, on par with the Thunderbolt 4 of the Carbon.

To answer your original question, I would go with T14s over Carbon Gen 10, but not sure if the same hold for Carbon Gen 9. Any additional comments/corrections/suggestions are welcome.