Death penalty is a bit different from summary execution.
Chinese intelligence executed 30 operatives? Good thing we have a decentralized unaccountable police force larger than ALL national armies to carry out summary executions to the tune of 1,000 citizens per year and save us money.
I'm not in favor of that either.
And its still apples to oranges. A police shooting in the moment is much different from a planned and televised execution.
In terms of time and money, indeed, the difference is as what you said...
But in terms of information flow, the difference would be quite huge...