Thermaltake Core V21 is the most customizable PC case that i know of and i don't think the cable management in there would be harder than inside regular tower type cases. Actually, i think it would be easier since you can remove all from it until you're looking the bare frame.
About air flow. Since Core V21 is so customizable, you can put up to 13x 120mm fans into V21 and create your very own specific airflow path. I don't know any other micro-ATX case that comes near to that.
As far as mobility goes, Fractal Design is like a small tower while Thermaltake is a cube. I find the cube to be easier to carry around than a tower but that's personal preference. Oh, Thermaltake is also 400 grams lighter.
Few specs:
Fractal Design,
Case dimensions - with feet/protrusions/screws: 413 x 210 x 412 mm
Net weight: 6.9 kg
link:
http://www.thermaltake.com/products-model.aspx?id=C_00002559
Thermaltake,
Dimension (H x W x D) - 336 x 320 x 424 mm (13.2 x 12.6 x 16.7 inch)
Net weight: 6.5 kg / 14.3 lb
link: http://www.fractal-design.com/home/product/cases/define-series/define-mini-c