Eleven pages isn't enough for a versus thread now? Oh okay then.
I think this is an interesting versus because of the strengths of each side, and think each side has a chance. Its certainly not a walk in the park for anyone. A few points:
Numbers way, way, way, way, wat, way wrong. Here's a quote from the canon
Dark Empire Issue 3:
Assuming a total war setting in which each system is producing 3 million clone troopers a year (as per your comment):
3,000,000 x 12,000,000 = 36,000,000,000,000 clone troopers a year.
(That's a little bit more than the unfounded 1,380,000,000 some people were throwing about the thread earlier).
If each system is mass-producing millions of droids a year too (again, remember in the OP that Palpatine's absolute goal, above-all-else, is The Golden Throne, he will use every resource to achieve this), this could take the number of troops to 100,000,000,000,000 per year. Now its starting to look comparable to 40K.
Now, going back to
my planet-killing starvation strategy.
Lets assume we have the four planet killers in operation: Death Star; Death Star II: Eclipse and the Sun Crusher. Following a scouting mission to get an Imperium starmap and identify Holy Terra's farmworlds (which are, I assume, in travelling distance of Terra), they would have a list of targets. Would such information by classified?
Hyperspace is much faster than Warp travel. Say the four superweapons targeted a solar system each every four hours. Say that four hours is estimated travelling time, firing, and jumping back out.
That's eighteen farmworlds and six solar systems destroyed each day. That's 168 farmworlds a week, and 672 a month. How many farmworlds is Holy Terra dependent on?
How much of this will the Psykers foresee? Can they identify the absolute order of planetary destruction, the trajectory in which the superweapon will exit Hyperspace into a system, fire, and be back in Hyperspace ASAP?
This strategy is a guess (though almost certainly not as smart) as to how Grand Admiral Thrawn could respond to this war situation. Yes he wasn't a fan of superweapons, but in this scenario (to achieve the Emperor's goal at any cost) he would choose to use the Empire's strengths (quick mass planetary extermination) over combatting the Imperium on their own strengths (insane capability for ground-based combat).
For the Galactic Empire to win this, they need to be using the considerable ship-building capabilities of 12-million effectively enslaved worlds, their superior targeting and speed capability, and their unique superweapons. If the GE has superiority in space, they've won most of the battle.
As per my proposed idea, if Holy Terra is deprived of food and its troopers starved to death, then its simply a case of wearing down the land-defenses of the more specialist units (Space Marines, Terminators, etc), millions of billions of troopers will die doing this, but with no external resources to support them, it will be a solitary Holy Terra versus every resource of the SW Galaxy. I assume the latter would win.