Shouldn’t your designs be speaking the same language as the code that’s implementing them? Yes, yes they should. And engineers use points, not pixels.
Kurt Varner digs into the reasons for designing at 1x over 2x. The post touches on all of the key arguments and feels compelling enough for designers working at 2x to consider changing their workflows. The key here is to make sure your whole team can buy into a 1x workflow. That's easier said than done, of course.
I finally made the leap to 1x this year and it feels great. Less mental math, better performance in Sketch, etc. All my projects now start at 1x on a 4-inch screen. Why? 1x for all the reasons Kurt has listed above. 4-inch because Apple is clearly investing in smaller, cheaper devices both in the US and abroad. I'd rather build products knowing that the design will work well within a system of greater constraints (and internationally, where smaller devices are more common). Scaling up after the fact is easy.