Everything dissipates heat. Question is, how much (and,
if you're curious, why).
A properly designed buck converter spends almost all
of its time conducting at low voltage drop across one
switch or another. Note that on old school, high voltage
output types the "switch" may be a diode on the low
side. At any rate you're talking a volt or less @ Imax
in either state, and switching accounts for some small
fraction of the period (during which you will traverse
a region of dissipative conduction).
Meanwhile your linear has no choice but to drop all
excess voltage (@ current) as heat. Not -a- volt.
Tens or more, quite often.