The X1 has soldered on memory. And non-user-serviceable batteries and hard drives. (My 1st gen X1 carbon used a very non-standard hard drive.)

The T460 has hot-swapable batteries, real memory slots, and standard SATA disks. (but I wish is was a NVMe disk)

I picked a 460 over a 460s because it seems a lot more servicable in the future and I can easily replace worn out batteries.