Hey RossMAN.
I've taken the family to Orlando 3 times in the past 2 years and I love Disney World as much as they do. Maybe even more. The first 2 times were when we still lived in Southern Oregon. We actually made the drive to PDX the first time and SFO the second time and got flights for $200 each instead of the $500 each it would have been from Medford. With 6 tickets to buy, it was worth the 5-6 hour drives. Then we drove down to Orlando from our new home in Charlotte, NC this past December.
Our first trip was in April/May. There were a couple days that got close to 90, but most days were in the low 80s. The second trip was in March/April. Temps were a little cooler. Mostly upper 70's and low 80's. Our last trip in December was great if you don't care about swimming. Temps were in the low 70's and evenings were just chilly enough for sweatshirts.
Overally, March/April weather was the best, but it was also the most crowded trip with lots of schools off for spring break and easter break. Crowds in April/May were definitely lower and temps were warmer. December crowds aren't bad at all until a couple days before christmas.
How long of a trip are you planning? If you have the time, I'd definitely recommend doing Universal and Disney. But if I had to pick only one, I'd go with Disney. There is just so much more to do and see.
If you don't know about it yet, there are some great sites for Disney related information and hot deals:
www.disboards.com
www.mousesavers.com
Ever since my first trip, I've spent a ton of time on the disboards and a ton of time planning our subsequent trips. So if you have any questions, I'm sure I can answer them. I'm enough of a Disney nut that my wife has pretty much banned me from talking about it at home.
EDIT: Oh yeah, and October is still hurricane season, just so you know. And from what I've heard, it can still be quite hot, if that's something that want to avoid.