Pictures begin below the fold.
A basic picture of the two dolls standing together. Most of the joint differences are visible here, even if it can't be seen how flexible the joints are/aren't. Body 3 is on the left, Body 4 is on the right. I like the extra waist movement in Body 3, but I like the head movement, more attractive joints and wrist movement in Body 4.
The biggest problem I had with this picture is trying to get the dolls to stand/lean while bending their arms. I didn't get as much of Body 3 (Melanie's) elbow joint as I should have. The fact that I only have one working stand and that I find the stands very fragile wasn't helping me. There's really no way they can stand by themselves on those tiny feet. Body 4 (Lindsay) is showing off how her wrist can turn.
This is the best picture I could get at the time of the girls in profile. I'm still not sure if they have exactly the same face mold. Getting all the hair away from the faces was not easy, nor was trying to give my daughter enough room to get in to take the picture while I held the girls' faces and hair.
And here's a view from the back. Melanie is more "endowed" in back than Lindsay. I find the screws unattractive, though, but they shouldn't be an issue. From the back, the girls' knee joints aren't that different in attractiveness.
Honestly, I wish Jun Planning could have taken Body 3's twist 'n turn waist and given it to Body 4. Other than that, I find each doll has enough pluses to make them both worth owning, especially since I was fortunate enough to get a number 3 body with no chips or cracks. I think these two are becoming great friends, and that more of them will be joining our household! And of course they are both insisting that they need more clothes. :)
If there's anything specific you want to see about these dolls, let me know! I'm hoping I'll get some photos taken during the weekend.