For non-competitive riding, it may not make much difference.
I've been very happy with the 11-speed shifting. That may eventually be replaced with 12-speed or 13-speed, but for now the 11s is still a mainstay. But, I would expect a few hundred discount for 10-speed shifting (unless you should choose 10x3 which is generally not supported with 11s).
And an upgrade from 10s to 11s may not be as simple as one might hope.
If you buy a "NOS" bike, you may get the factory warranty, while a used bike generally will not have a transferable warranty (beyond what your shop gives you).
The warranties generally don't cover crash damage, but may cover factory defects (which are generally rare, but can show up as a design flaw that became obvious later).
I personally haven't jumped to electronic shifting. Your Di2 bike could be a very expensive bike. However, if something goes wrong, it could become a nightmare. Is the battery good?