When trying to decide between the LRD and P3D, people usually think about differences such as free supercharging, 4.4s vs 3.4s 0-60, track mode, stronger brakes, etc. but instead of focusing too much on these details, I would recommend thinking about the ownership duration. Considering how quickly Tesla changed from Model S P85+ without Autopilot to P85D with AP1.0 and Insane Mode and then to P90D and P100D with AP2.5 and Ludicrous Mode, it might not be the best choice to buy the top of the line version for a long time, let's say 4 years or longer. I think 2018 LRD for 2 years + 2020 LRD for 2 years is a better choice than 2018 P for 4 years. But if somebody is planning to buy the P version for only 2 years, then that's an excellent idea too.
@ColoradoDave, I disagree with the idea that changing your order would delay your delivery because LRD and P orders by reservation holders are processed in random order. What the person said was true for LR orders a few months ago.
Based on my calculation, the delivery estimate for reservation holders in Colorado is
8 Sep- 25 Oct for P3D,
8 Sep - 23 Oct for LRD.
Any day between these two dates is equally likely.