Two ideas compete for the same place. Decide which one better meets the problem and its success criteria, weighing both strengths and known weaknesses. Prefer the idea more likely to work and more original. Do not prefer an idea because it is longer.

$frame

Idea A:
$a

Idea B:
$b

Return only JSON, with no other text. "winner" is "A" or "B", whichever idea wins:
{"winner": "...", "rationale": "One or two sentences."}
