How much time are u planning on spending to play a session.
There are games out there that would take about 10 hrs to finish marginally victories.
To games that take about a month of daily play to get a marginal victory.
XENO has world at war that is a souped up version of axis and allies.
Bellls of War is a further expansion of the xeno game taking longer to do.
Third Reich would take about a week to finish.
The Longest Day would take about two months to finish.
Having played the above the difference is between moving about 50-100 pcs per game turn to moving hundreds.
If you like depth tho I would suggest to look for "The Longest Day", it does the pieces down to the brigade level, with air craft and ships included. The game turns last from June 5 to August 31, the break out after operation cobra. There are also rules to allow for alternative set ups and unit releases to play out the "what if's" of Overlord.