The Empire had no local partners on Hoth, and Vader commanded a large personal armada that was nonetheless barely adequate for the daunting task of completely blocking off both Hoth’s surface and orbital expanse. A much larger ground force with air superiority met with similarly subpar results during the Clone War’s Battle of Geonosis. In contrast, all the Rebel Alliance needed to do was evacuate its elites and reconstitute its forces elsewhere. As Graham Jenkins points out in this roundtable, the Rebels deserve credit for their tenacious — and effective — delaying battle.
Ackerman’s analysis is here.