Upgrading a Commander precon, or tuning a 60-card list between events? Put the two lists side by side and see exactly which cards went in, which came out and what it costs to get there.
Deck A
Deck B

A new commander is listed first, ahead of every other change, because it changes what the whole deck is. Partner commanders are tracked the same way.
In 60-card formats, a card moved between the main deck and the sideboard shows as a move rather than one card removed and another added, so a sideboard plan reads at a glance.
Swapping a card for a different printing, or a non-foil for a foil, is a printing change: the card count stays the same, and the upgrade cost prices the printing you chose.
Avengers Assemble against its Collector's Edition: the same list of cards, so the comparison is almost entirely printing changes.
Open this comparisonPick the precon as deck A and your deck as deck B. The added cards are your upgrade, and the upgrade cost is what they cost today.
Yes. Commander and partner changes are shown at the top, ahead of the card changes, so they are never lost in a long list.
Yes. Search community decks by name, or by commander with hero: followed by a name, in either slot.
More in the deck compare FAQ.