I have stayed at both but we have gone back to the Maui Banyan for the last four years.
If you are pool people the pool at Kahana Beach is terrible. The Banyan has two nice pools with a hot shower.
One of the nicest beaches in Maui is across the street from the Banyan. The beach in front of Kahana is okay...has lots of big sea turtles.
But if you want OCEANFRONT Kahana Beach is for you. I was told it is the closest oceanfront hotel on the entire island of Maui because when it was built the building codes being that close to the ocean were different then they are now. You open your lanai door and hear the crashing waves all night. (We were on the first floor). About half of the timeshare units in The Banyan have a parking lot view so definitely call to request a garden,pool view room if you decide to stay there.
Both are clean, comfortable hotels.
There is a bypass road to Kahului from Kihei if needed but Kihei has everything and Wailea is about a ten minute drive.
Also depending on what month you go the weather in Kihei is sunnier and drier.
The parking at Kahana Beach is terrible whereas the Banyan has a nice parking garage.
This website might help. You will see in the picture of the Kahana Beach how close it is to the water.
https://www.soleilmanagement.com/properties_listings.aspx
We head back to the Banyan for the fifth year in a row in November.