Two factors seem different to me this time. First, the MCO made higher highs this time (while the index didn't) which I interpret as a sign of increasing momentum on the upside. Second, the 10% Index finished at +668 which means that market breadth is very strong to the upside and that after any interim correction prices will move higher. At the previous MCO peak at +250 the 10% Index failed to get above +500 -- indicating that fewer issues were participating and that sentiment towards stocks still remained weak with sellers rushing in to unwind long positions. The initial MCO spike to +250 was probably short covering.
I would also note that sentiment measurements (AAII, II etc) are still bearish indicating that this rally has a ways to go on the upside.
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