Here's a little comparison I put together for most of the replacement 1/6 scale bodies Pullips use. You can see them below (click the picture for a much bigger version)
From Left to Right: Volks EB Beauty, Obitsu Hard Bust, Obitsu Soft Bust (new type) Pullip Type 2, Pullip Type 3, Pullip Type 1, Obitsu 25cm, Obitsu 23cm, Dal body.
Volks is the tallest body by about .5cm. Dals are about the same height as a 23cm obitsu, there's maybe a few millimeters of difference.
Let's start with the 'kid' bodies.
25cm Obitsu, 23cm Obitsu, Dal body
The 25cm body is very straight, a real teen body. You can get larger boob sizes, but as the chest piece is so high on the torso they can almost seem to come up TOO high. The 23 cm is a very straight kid body. Almost flat, but not quite. This one only comes in one chest size. Dal has a more mature, curvy body. Dal also has a tendency to be extremely white. The 23cm has been massively toned and still looks very orange on Noirette, Fiori, or most of the other Dals. Hard busts are easier to tone than soft busts, so keep that in mind if color differences bother you.
The 25cm is the only one who can cross her ankles.
All three dolls can cross their legs if you turn the knee joint. This shows the limit to which the knees can bend also. The 25 cm has a 'new' knee joint that bends much further than previous knee joints present on all 27 cm, 23cm and 21cm bodies. The dal knee barely bends.
Bending forward: Dal barely does, the 23 cm can go a little further than Dal, and the 25 cm can bend slightly more in the torso (which causes torso squishing) but mostly in the neck due to new neck and torso pivot joints present in the 25cm.
Speaking of necks... there is a slight gap on the 23cm when put on a Dal head. If you put the head on snugly (the Hard Bust obitsu tutorial applies to 23cm bodies) this is as bad as it gets. If you don't clip the neck peg before you shorten the piece that goes on top of it there is a wider gap.
But that gap is nothing compared to this gap! Dal necks sit againt the head like type 1 pullips, not inside the head like type 2 and 3. When the neck is straight there is not much of a gap, but when the neck bends, there is a HUGE gap.
And here's that tummy thing I mentioned. You don't have to bend the doll far to get it. The 27cm soft torso is a litle more rigid; it also folds like this in extreme positions, but it doesn't bend quite as much in the regular range of positions like the 25cm does.
Onto the 'Adult' bodies:
Volks EB beauty, Obitsu hard bust, Obitsu new soft bust, Pullip Type 2, Pullip Type 1, 25cm Obitsu, Pullip Type 3
In this series the Pullip head is on the 25 cm body instead of the Dal head. The match is better because pullip has a darker head on average, even though she is never as orange as the Obitsu bodies are.
The heavier pullip head pulls the forehead all the way down to the knees. The soft torso 27 cm can almost do this, and is about the same as the Pullip type 2. The original soft torso obitsu series is about the same as a pullip type 2 as well. The least torso-flexible doll is the Pullip type 3. Pullip type 1 is about the same as Volks, and Obitsu hard busts are in between the type 1 and volks and the soft bust bodies.
The only dolls that can cross the ankles are the 2-part soft torsos (the 25cm and the 'new' soft torso obitsu) The only doll that can't fake crossing her legs by pivoting at the knee are the type 1 pullip. The least flexible knee joint goes to the Type 3 pullip. Surprisingly, the most flexible knee after the 25cm is the type 1 pullip. The rest vary in their ability to bring the calf to the thigh as you can see.
The way the neck fits is different on all of the Pullips. Type 1 pullips have a similar problem to the Dal heads. Type 2 (pictured above) has a gap around the neck, but it sits inside the head so when the head is bent you can't see it (see below). The type 3 head fits snugly around the neck and has no gap when bending.
Overall, the 25 cm body can be used with either pullips or Dals to create a teen doll. Pullips are more similar to this height in stockbodies than they are to 27cms and so look a little more proportionate, as well as having a better chance of tone matching.
Beyond that, what kind of body you choose for your Dal or Pullip depends on what you look for most in a body.