In what ways were these forces larger, or smaller, than those the Japanese had in motion on December 7, 1941?
I would have guessed, all told, they were roughly the same.
The Japanese force attacking Pearl Harbor did not include an invasion force. That alone makes the Midway force larger. That aside lets look at some particulars.
There were 6 front line carriers involved at Pearl. 4 of the same carriers were involved at Midway. Additionally, there were another 4 carriers of smaller caliber involved in this attack. All told, carrier compliments were about the same.
However, there was not nearly the surface compliment involved in Pearl Harbor as there was at Midway. Here we have sea tenders carrying midgets subs, a screen of submarines at about the same levels, 4 times as many cruisers, 3 times as many battleships, and a load of destroyers.
Pretty much the bulk of the Japanese fleet was committed to this attack, while when the Pearl Harbor attack took place the Naval General Staff still had enough sway over Yamamoto to keep some naval forces tied up in the southern advance. After the success of Pearl, Yamamoto pretty much had carte blanche.