OK, I'll take the middle of the road--I usually buy both the Unofficial Guide (which is my #1 pick without question) AND the Birnbaum's book
The Unofficial guide is great, and I won't go into further detail. But, if memory serves, most recent version was published just before the return of Early Entry. So I don't believe you will find reliable info regarding days to visit individual parks. But don't let that sour you. In most other regards, it's invaluable.
The Birnbaum's guide is the "official" guide to WDW, so it tends to give you more of the company line as Matty said. But I still found a lot of valuable info, and the color layout / photos makes it easier to discuss specifics with your traveling companions.
Check out the web site:
www.tourguidemike.com
This site is fairly new and still a bit disorganized, but if you really dig, you'll find a lot of other valuable tips. My main beef with this site is that it gives you the impression that by plugging in a lot of your trip info, it will create a custom itinerary for you. That's not really true. You can tell it which parks, attractions, restaurants you want to visit and it will help you put that info into a managable agenda format. It will also give you recommended visitation times for specific attractions. So, in a roundabout way, it does to what is promised.
But, it's not as simple as saying "I want to ride TOT, Star Tours and Indy Jones on Tuesday, with lunch at H&V", and you suddenly get a minute-by-minute schedule for your day.
To actually answer your planning question, I typically split our trip into half-day blocks. With a toddler son that needs a nap, it's a forgone conclusion that we have to return to the hotel around 1pm daily. So, I'll plan on a specific park visit for the morning and another for the late-afternoon/evening. That gives me enough info to make Priority Seating, and ensure that we hit all of the parades / night shows that we really want to see.
I will typically educate myself with regard to the best touring plans (eg. at the MK, Fantasyland first in the am, and so on), but that's nothing that I put in writing.
If you're going in September / October, the crowds should be very managable. Using FastPass, you shouldn't have any problems at all with ride wait times.
As you're trying to make a final decision, make sure the weather is a part of your considerations. We have visited WDW twice in late September, and now know that it's just too warm and humid for us. Both trips the temps hit the 90s and the humidity was HIGH. It's also hurricane season, so the chance of rain is that much higher.
The later you go into October, the more temperate it will be. I hope I'm not coming across as a "wimp", but the reality is it's a whole lot more comfortable walking around for a week in 80 degree temps than it is in 90 degree temps.