I agree. And personally I would never place market orders. But sometimes you need to get out of position quickly, and this is when market orders can be useful. My point was that SPY is probably the only product where you can use market share orders on some extreme cases, and get away with it with relatively small damage. It is not possible with SPX or any other underlying.
Normally SPY options are treated as short term gains (vs. SPX that gets special treatment), but LEAPS can be treated as long term gains if you hold them more than a year. At least this is my understanding, but I'm not a tax expert so I can be wrong.