Looking at these numbers, you can deduct the following:
Act1: 41.3% chance of getting iLvL 61 or higher per rare drop.
Act2: 51.2% chance of getting iLvL 61 or higher per rare drop.
Act3/4: 65.1% chance of getting iLvL 61 or higher per rare drop.
Your numbers are correct, but if you are farming you don't want just any ilvl 61 or higher. Ilvl 61 weapons generally don't sell at all on the AH, and ilvl 62 weapons sell only in certain specific situations (mainly as stat sticks). Ilvl 61 armors sell for very little. The best loot is ilvl 63 weapons and ilvl 62/63 armors, and if you count only those there is a HUGE difference between acts.
probability of getting ilvl 62 or 63 on armor drops:
probability of getting ilvl 63 on weapon drops:
probability of getting the above mentioned when half the drops are weapons:
A2: 18.6% = 67% more than A1
A3: 27.2% = 145% more than A1 (46% more than A2)
For somebody like me who has previously done endless A1 runs its pretty obvious: A1 weapon drops truluy suck. The difference in later acts is simply amazing.
Based on my numbers, if your kill speed in A2 is at least 60% of your A1 kill speed you should farm A2. If your A3 kill speed is at least 40% of your A1 kill speed, farm A3. Also keep in mind that A3 in general is very densely populated compared to the other acts, so there is minimum runtime between elites. For the WW/sprint build this is a major advantage.
Another thing worth considering is to roll A2 in full MF gear. This requires considerably less armor/resists/dmg than doing A3, so it can be done with reasonably cheap gear.
These are good, but you should note that your #'s assume that you have the same MF % in all acts. Unless, of course, you don't care whether the items are white, blue, or yellow.
Also, once you start changing the MF%, you would need to factor in the % chance of getting 6 affix, 5 affix, etc. and I don't think we have those actual figures.
Unfortunately, the issues that I pointed out are the reason that we can't seem to get any truly accurate answer on this issue.
statistic has no mercy - if you kill twice as many (or as fast) on act1, lvl63 drop is same in number. that's why act2 is bad for farming - too slow and exp is the same. act1 needs four times as many as act3 to be equal, which is simply too much - likely you'll be faster than that.
with right gear, act3 is a place to go
in any other case, act1 gives more experience and still doesn't rule out getting 63's
Rollback Post to RevisionRollBack
A proud and fearless leader and only member of the "Save the Diablo III" project I have been a game designer, modder and balancer. Link below is to my blog, where i discuss flaws of this game and offering solutions.
YOU can help this cause by sharing a link in your signature! Please do, if you like my ideas http://savediablo3.wix.com/diablo3#!home/mainPage