Lets do the math on what Fishijie does. A bomber can sometimes remove 2 hp, but usually just 1 and also there are times that the bombing mission fails. Enemy city has 2 veteran Infantry, 2 regular Infantry and a regular MDI. 17 hp needing rid of before everyone is dead. If 20 bombers all have successful attacks(unlikely) they might clear this city of units(bombers don't always hit units anyway, they destroy buildings and kill citizes too, about 33% per option plus the chance of failure). Assuming horrendous losses, 10 unsupported tanks could take the same city if they were pre-positioned. With artillery redlining all defenders, 5 tanks could do it with posibly no losses. Bombers just are too hit or miss for my liking. I'm sure the hardcore can't be convinced either way, but I am.
Well, I don't think this is quite fair, either. Bombers do have a ROF of 3, not 2, and as I said, I think the average hit value is somewhere between 1 and 2. Let's assume 50%, or an average damage per attack of 1.5. There will sometimes be "waste" (a bomber gets 3 hits, but the attacked unit is redlined), so assume the 17 hp of needed damage is effectively 21. That means you could do the job with 14 of those bombers, and the other six could do something else. Of course, you haven't actually taken a town this way, just opened it up for a unit - but it could be a lowly warrior, if one starts close enough. More likely, a cavalry or tank unit does the actual capture. There is some chance for losses, if the AI has acquired flight.
In your tank battle against units on grass, according to a combat calculator, you could expect to lose two units, and severely damage one and lightly damage one more. If the defenders are on a hill, you would expect to lose a third unit, and have two other damaged to some degree. So you'll probably have 4-6 tanks that remain available for use elsewhere.
Now figure the combined arms approach: 12 artillery, 4 bombers, and 6 tanks (which is actually slightly cheaper to build than 20 of the others, especially since you probably got the artillery through upgrades). Artillery only has a ROF of 2, so with 12 you'll probably get 10 or so damage - say two redlines, and the rest damage results. Now use two bombers to take out the two units with the highest remaining hp. Now you need at most 3 tanks to finish the job. (Probably only one of the tanks even takes damage, but it is very doubtful that you lose any.) Now you still have 3 tanks and two bombers to use elsewhere, and you still have all the units you started with to use the next turn, except perhaps one of the bombers, if the AI has flight.
I'm going with that last method, myself.
