Kiki's is slightly longer on her but they're not that close - here's a side-on shot of Casper's


And Kiki's

(I have noticed that Cain seems to be missing part of his back legs, not sure what happened there!)

I think as Kiki has such a deep, long chest, hers naturally sits further back too - you can see the strap at a shallower angle than Casper's, as his chest finishes shorter on his body.