Aida wrote: "Jonesy, from the front I like the smaller; from the back and side the larger (and sometimes the smaller, I go back and forth -_-). The concern is that slouchy pants shouldn't really look like they pull across one's seat, and I can't tell if these do or not! Not sure track pants should be highlighting that, anyway I have been thinking that maybe the perfect size for me fall right in between these two. As I said above, the smaller size feels more fab because it's less baggy, but the larger size seems more "correct" for this style of pant."
Aida, I also felt with the Leith pants that I fell between the two sizes I ordered, and you describe the differences as I would. I just decided to keep them both and wear them differently depending on my mood and my topper. If I had to absolutely choose one pair for me, I would keep the bigger size, even though it as loose on me as you describe the larger size is on you, visually it is not a big difference between the two, but one the wearer feels. I also need the extra leg length that I get from it, but that isn't an issue for you. I wear the larger size up on my natural waist where it could be gently tugged right off -- but I decided with that wide elastic waistband (even though it did gape a bit untied) they wouldn't exactly fall off in reality; and the smaller size I wear on my high hip. With you being petite, I am not sure if this works as well for you. I also feel, as you do, with this style pants that if I had to err, I should err on the side of looser/slouchier when in doubt. But bottom line is I couldn't decide, I kept going back and forth, so I kept them both just in case and plan to wear them both. The price point of these pants helped with making that decision.
ETA: These pants look absolutely fantastic on you and I love the leg length. After really studying your photos, I would go with the bigger size if you had to keep the one pair. But I think you should keep both for their slightly different profiles and feel.