Rental cars for stops in Kauai and Honolulu

I read that it is easier to grab a taxi to the airport to pickup our rental cars than try to get anything closer to the ports and that the 'free' pickup offered by some companies is not worth it.

Any opinions on this.? Bear in mind we will be in Honolulu on Sunday Nov 11 and Kauai on Monday Nov 12 which is a holiday weekend so ...?

We've taken the free rental car shuttle twice on Kauai and had no issues. We used Hertz both times. Honolulu if I remember right, you would take a taxi to the rental car office. For us, again we were going to go with Hertz. They were going to reimburse us for the cost of the taxi. We ended up getting the taxi, but never went to the rental place because the taxi driver took us where we wanted to go and it was cheaper than renting the car. Our plan that day was to go to Hanalei Bay and snorkel and that was it.