Both have 8th generation Intel CPUs inside, only with a small difference in clock speeds (and if that even makes a difference in practice due to the thermal constraints, remains to be seen), and the only other difference is the keyboard with potentially a lower failure-rate, but if you ever do have a failure, then you're getting the new keyboard anyway as a replacement, so I'd say that's negligible.
So with a $250 difference, I'd probably opt for the 2018 model if I'm honest, unless you really really need that tiny extra bit of performance for your needs. Though you could always wait for the first benchmarks and reviews to be sure that there's nothing else you're missing out on.