There's an area where you look big? I sure don't see it! But truly, I get what you're saying - I pulled out my Leith track pants to wear today (after wearing them a ton last year and not at all this year) and they have the same look from the waist down as your jumpsuit. I am super sensitive about the appearance of my lower half, and no one sees what I see - I think I am looking through a fun house mirror.
I like it best unbelted and long, although belted looks good too.