Which of the following structures would be least stable?
I initially approached it like this:
As both are allylic carbocations, and that both are in fact resonating structures of the same molecule, so resonance can't be used to judge them. So I went for hyperconjugation. The first molecule has four alpha hydrogens and the second has only one alpha hydrogen.
Since there is more hyperconjugation in the first, it should be more stable. But I also have an intuition that there might be something more that we should have a look upon but I'm not able to figure it out. Should we always choose hyperconjugation as our second option when we can't make judgements using resonance?