Hello Donna!
I've stayed "off-property" before in a condo about 10 minutes away from the Walt Disney World Resort property. We definitely enjoyed the extra room we had a the condo and having a full home to ourselves to spread out and relax in at the end of the day. We were traveling with a large party and it was great to have lots of room for everyone.
That being said, you do lose out on time. Although the travel time on the GPS stated we were only ten minutes away, it took much longer than that because of traffic lights, traffic jams, having to park the car, ect. We enjoy being able to take a midday break to nap or swim, and we weren't able to do so with staying offsite.
You will also miss out on other
benefits, such as Extra Magic Hours. Each day, one of the four Theme Parks will open an hour early or stay open three hours past "normal" closing time. During these times, only guests staying at select Walt Disney World Resorts will have access to the parks. While we don't normally use the Evening Extra Magic Hours, we almost always take advantage of the Early Morning Extra Magic Hours. We are able to see and do a lot before the park opens to other guests!
However, no matter where you stay, you'll have a magical vacation! You can most certainly have a fantastic time and see and do tons event without using Extra Magic Hours! Don't let that discourage you. Just make a plan to make the most out of the time you do have at the parks and you'll be feeling the pixie-dust in the air.
Please let me know if there's anything else I can do to help you make the most out of your vacation.
Have a Disney day!
Ashley