Smart decision, assuming you wanted your truck sometime in the next two years. Congrats on the order.
I think for most, the max pack is overrated and not necessary. 300 miles is still a ton of range. If you get the 21's, it will actually get close to the range it says it will in moderate temperature climates.
400 miles would be nice for those that tow regularly or travel long distances regularly in colder climates. But, beyond that, the extra range really isn't necessary. $10,000 more and most will never use it. 300 miles is about 5 hours of driving. At least for me, my bladder usually won't last that long, thus would be stopping anyway. I don't tow very often, if ever. Most of my road trips are in the 300 to 500 mile range. I'm always stopping at least once on those trips anyway.
So at least for me, if I had 400 miles in range, I really wouldn't benefit anything from it. There's also something to be said for arriving at a charger with a lower battery percentage as it will charge quicker. With a 400 mile battery, would arrive at the charger (because of my bladder stop), with more percentage of range which would lead to slower charging.
Of course there are plenty that would actually benefit from the extra 100 miles in range. But, I think most have no real "need" for it and 300 miles will satisfy their needs in almost every situation.
