As PP said, you want to have both apps on your phone.
Sometimes one will be cheaper than the other.
Sometimes one will be faster than the other.
If you are trying to get a ride at a theme park after the fireworks, keep in mind that many other people are trying to do the same thing.
You should download the apps and set up the accounts while you are home. You will have to enter a bunch of info, including credit card info. It's easier to do that at home rather than when you are out in public in the dark.
After you download the apps, you can link each to a rewards program, such as an airline or hotel frequent flyer/stay program. So if you need to book a ride, and you check both apps, and one won't get you to your destination cheaper or faster than the other: you might want to use the one which gives you rewards toward the program you prefer.
Uber:
Account
Settings
Rewards
Lyft:
Use the pull-down menu at the top left of the screen
Rewards
You can practice using the apps while you are home. Just remember the "location services" feature on your phone. On an iPhone, it's in Settings, then Privacy. I don't know where it is on an Android phone. If location services is on, the Uber/Lyft app will think you want to be picked up where your phone currently is. If you want to practice, you need to tell your phone where you will want to be picked up (Epcot, for example) so it doesn't think you are trying to get a ride from your house. You won't get a good sense of the number of drivers around, or the cost, if the app thinks you want a ride from your house to the Orland-area hotel!
If you are someone who normally has "location services" turned off:
You need to turn it on to link a rewards program to Lyft. (You can turn it right back off if you want.)
It's easier to use Uber and Lyft if it's on, so you might want to have it on during your vacation.
