However you do the math, it means three things:
1: This point is nearly inarguable, tanks are strictly worse than they were in AA50. The only advantages they receive is the ability to attack on 4 with a fighter (This will likely have very little impact), and the ability to carry along a bullet shield two spaces for 4IPCs in the form of MechInf (which may prove more useful).
2: An equal IPC stack of infantry on the attack will win 54% of the time at 6IPCs, and the limit of this figure aproaches 100% as the IPC value aproaches infinity. By only 24 IPCs the odds are 67% in favor of the attacking infantry. If the infantry defend and the tanks attack, the figure is, obviously, even more skewed in favor of the infantry. Thus, if only one space of movement per turn is needed, tanks are strictly worse than infantry.
3: Another two-movement land unit can now be purchased for 66% of the cost of a tank. The MechInf is significantly more cost effective on the defense than a tank, getting the same average number of hits per IPC while costing only 66% as much for 1 wound. Thus, tanks are not useful on the defense in any situation, only in an attacking scenario. The tank does provide an attack value of 3 for 60% of the cost of a fighter, and has twice the firepower per IPC as a mechanized on the attack. However the fighter is much more mobile, is more powerful on the defense, and has the flexibility to participate in naval combat. That doesn’t mean tanks are useless compared to fighters, you can buy a hell of a lot more for the same amount of money, but it does restrict tanks to a much more niche role than before. Tanks are not cost effective for a slow moving attack, infantry are much better for that. Tanks are only effective when you need both to be able to move quickly, and focus on offense much more than defense.