The thing about the Las Vegas airport is that you must take a shuttle to get to the rental car center. With Verve (or Economy Rental, as I booked it), you have to take ANOTHER shuttle from that rental car center to an even further off-site location at some strip mall in the middle of Vegas. In our case, we had to wait outside in the dry 90+ degree heat for this second shuttle to come, and it took a while. This second trip will add a significant amount of time and inconvenience to your transit time. Because of this I regret renting with these guys and do not recommend them. All other aspects of their service are completely irrelevant. Book with a bigger rental provider even if you have to pay a little more because that second trip is such a waste of time and effort.
Btw, maybe I will comment on their service. When you return the car, you do so "in the back of the building" where there is a group of sweaty, angry, untrained, unprofessional, disorganized kids waiting to receive your car. Not the best environment to cap a vacation that was otherwise pleasant.