I always book on Costco too. And prefer Alamo. We pick up car in Ft Lauderdale, we fly there to visit family first, then drive rental up to Wdw. Lots of tolls between Ft Lauderdale & Orlando! So I prefer Alamo. You can drive thru tolls in Sunpass Lane. They cap admin fee at a reasonable limit. Since we're there 10 days that's a good thing. Beware some of these so called budget companies. Their fees are higher than the major companies (Alamo, Budget,
Avis).
After we check into our resort we return car. Alamo is conviently located in 2 places in Wdw. Across from TTC and at Dolphin makes it very easy to return car. And the Car Care return across from TTC has shuttles, they will pick you up or drop you off anywhere on Wdw property.
Costco gives you one free extra driver too. Most companies charge $10/day for that.
Prices do go up & down. So freq checking is a must. We have a 10 day rental picking up in Lauderdale & dropping off in Wdw for $230
I've been checking the site and price is now $460!!!

$230 may be the best I can do for this year, we'll see. Last year I got it for $180. Sometimes price drops a week before or even days before. We leave in 2.5 weeks so I'm now checking 2x a day, lol. Morning & night. I've seen price drop at night, and the next morning go right back up.
Check with your car insurance if they offer rental insurance. We have a policy added on to ours with ICBC. It's cheap. Only $30 or $40/year. Rental companies rip you off. And credit card companies do have car insurance but not 3rd party liability so beware.