IMHO - Ultegra 10. Not even close. The major change for me on the 10spd side was the change in the feel of the shift. No comparison in my book.

As for 9 spd....as mentioned NOS 9spd stuff...and yes it is old stock now...is disappearing even faster by the day. Like 8spd before it you will find that the only replacement or repair parts you will be able to find when you actually need them are on e-bay, are used, and demand a premium.

Chains and cassettes will be around forever.

FWIW you can also run the same "mountain" setup with a 10spd drivetrain. You just have to go with aftermarket cassettes.