not a huge fan of how mass effect moved to thermal clips, but they could potentially still have a distinct advantage over traditional ammo: reusability!
I imagine they're packaged in crates with a bunch of portable radiator units or something, and once you've expended a thermal clip you can just stick it in the radiator, grab one that's cooled off, rinse and repeat. it allows you to fire at higher power in longer bursts than with an onboard radiative cooling solution.
sure, from the infantry's point of view it really is just going back to magazines in pretty much every way that matters, but it would be fantastic from a macro logistics point of view - you don't have to keep shipping ammo out, aside from the occasional crate of metal bricks.
