Passage Summary: Vacuum tubes are tougher against heat than semiconductors, but to be better for digital circuits, they also need to match semiconductors in other areas like power. Right now, vacuum tubes don't match that power.

Reasoning: Vacuum tubes handle heat better than semiconductors, but a component is only preferable for digital circuits if it also matches semiconductors in other areas like current capacity, which vacuum tubes currently do not.

Analysis: This stimulus sets up a conditional requirement: for a heat-resistant component to be 'preferable,' it must be comparable in all other significant respects. The author then provides a fact that triggers the 'not' side of this condition: vacuum tubes are not comparable in current capacity. Therefore, we can conclude that vacuum tubes are not currently preferable for use in digital circuits. Look for an answer that strictly follows this logical deduction without adding outside info.