This can be a long discussion.
First of all, all the rental companies use
ECVs that are designed for a battery life of about 25 miles on a full charge with someone at the rated weight capacity on the
ECV. The batteries are similar to car batteries, except they use a gel instead of a liquid and are spillproof. Car batteries, even new ones, can go bad even when they are fairly new.
In my personal experience I had sometimes had rentals that I would leave in the trunk of the car overnight and would have no problem getting two day's use on one charge. Since I have had my own ECV I had one of the batteries (which were new with the ECV) go bad after less than a year.
Therefore, the answer to your nervous question is that it does not matter who you rent from as far as reliability.
As to the other part of your question. Yes, Walker is more expensive that Randy but I am not aware of the exact price difference.
The key point, other than price, is that Walker will drop off your ECV at Bell Services before your arrival and pick it up after you have left. Randy's will want to deliver it to you and pick it up in person.
The advantage to Randy is if you are not familiar with ECVs the person delivering can teach you both how it works and how to disassemble or assemble it if you need to break it down.
The advantage to Walker is if you are arriving at night it will be there for you, especially if you are heading to a park first thing in the morning. Similarly, for departure you can be using the ECV until the time you actually leave, and then turn it in to Bell Services and it will get picked up.
Now you can get out your coin and flip it.