Good question, and I don't know the answer, but I would think it best, economically speaking, to initially go with the shorter bullet and see how well you are able to work it within it's limitations. There's a good chance you aren't good enough of a shooter, yet, to make the most of the longer bullets and the advantages they offer at long range. You can always have the throat lengthened later.

So... I would learn on the shorter bullets. If/when you find you are competitive at shorter range and not at long range, you may very well be "good enough" to benefit from the longer bullets.