Barbie, the 'standard' fashion doll size for over 50 years, has now evolved into 4 body shapes: Regular (I have since been told Mattel gave this size the more elegant name of 'classic'), Tall, Curvy, & Petite! Choice is good, but instead of fashions being one size fits all, they are one size fits...some?
Kind of like shopping for real girls, now!
Actually, it's still nowhere near that complicated, but but we'll get to that later. First, let's look at the changes:
Same picture as the previous one, but with reference lines added to help you see where the differences are.
Tall Barbie has a slightly longer torso and legs. Just a teensy bit. As far as getting clothes to fit, the biggest difference is her boyish figure.
Curvy Barbie is about the same height, just flat feet so she looks a little shorter. She has the same length torso, but is more pear shaped with a not much larger upper body but a bigger lower body. Her knees have also been moved to a higher, more natural location.
Petite Barbie has a slightly shorter torso and legs. Like Curvy Barbie, she also has shorter thighs. She has less of an hourglass figure, but is not very differently shaped/proportioned to regular Barbie.
Here are all the numbers broken down: 
You may be surprised by how many measurements are shared between regular Barbie and the new body shapes, and how close the ones that aren't shared are! I've mentioned before that variation of 1cm or less at this size can usually be taken care of by adjusting the back closure. What does that mean for doll clothes?
Petite Barbie, whose measurements are all 1 cm or less different, you should be able to use the same clothes and patterns but overlap/take in the back closure slightly.
Tall Barbie, whose waist measurement is over 1 cm different, will probably have trouble with non-stretchy Barbie dresses and non-stretchy tops. Low-rider pants that fit at the hips instead of the waist should be OK, but ones that go higher than that will be trouble. Some stretchy dresses may fit, but most will be a bit shorter. Curvy Barbie has the measurements most different to Regular Barbie and will be able to share the fewest clothes. Some very stretchy dresses and skirts may fit. She will have the easiest time borrowing shirts, provided they have at least a little bit of stretch.
By this logic, all Barbies should be able to share the same stretchy sheath dresses. Let's try that out: 
These are not factory made clothes, these are all the same dress made from my Cocktail Dress Pattern put on the different dolls. Theoretically this type of dress should fit all of them, and it does!
On Regular Barbie, the dress ends a bit below the knee. On Tall Barbie, it ends at the knee. On Curvy Barbie, it also comes up a little bit short because the stretch that allows the dress to fit her wide hips and thighs shortens the vertical length. On Petite, it goes down to mid-calf. The only major difference in fit is the length, which is the easiest adjustment to make to any pattern and any newb can do it.