Hmm, I am a K brand polygamist.
I started with a lovely Kanile'a, it is feather light weight, and has a gorgeous, stunning, UV finish. She has a tad bit of bling, with her gold tuners, and the K2 package features. I thought that was it for me. I took a tour of the factory in Kaneohe and adored both Joe and Kristen Souza. They have been so wonderful to me in each and every dealing I have ever had with them. I liked the fact that Joe was a firefighter (as I'm married to a police lieutenant). And I had a huge chip on my shoulder when it came to Kamaka, as I had a bit of the "Marcia, Marcia, Marcia" complex over them as a Kanile'a fan ("Brady Bunch" reference for you kids too young to know that).
Then I began to secretly lust after a Kamaka. It started innocently enough, I begrudgingly began to respect their almost 100 years in the business, and my two favorite uke players (Jake and Aldrine - who at the time was playing Mika) both played Kamakas. I am a huge fan of Hawaii as I have traveled their at least a couple of times a year since I was a kid and my grandmother's ashes are scattered off the coast of Kauai. So I decided I would save up to get a Kamaka for the historical and Hawaiian purposes, almost just as a collectible. But it couldn't be just any Kamaka, I wanted a curly one. After a lot of searching, I found my beloved Pele. I fell instantly in love with the feel of the uke, the playability of it, and the curl of the koa. Suddenly my Kanile'a sounded thin compared to the Kamaka's rich tones. Mind you, I got rid of those god-awful Kamaka strings. If there was one thing they could do to improve their sales, it would be that. Because I still believe that they lose so many people (particularly to KoAloha) in side by side tests in stores due to those things. So I bought Pele, and still love that uke dearly.
At that point, the collector in me began to rise up, and I decided I wanted to have a pineapple uke. I figured as long as I was buying a new uke, I might as well buy one from another K brand Hawaiian manufacturer, so there was only one pineapple that really stood out to me -- the Pineapple Sunday by KoAloha. It is a long and winding tale of how many PS ukes I went through (I think 5 was the final count?) before finding the right one for me, but now I have her. I think the KoAloha engineering designs allow for them to make simply spectacular ukes. Their volume, and tone and projection are (in my mind) second to none. If I had to get a uke sight and sound unseen, for the best quality sound, I would recommend the KoAloha. That being said, I think that the PS, while lovely, is not a very versatile uke. It is a bit uncomfortable for me to play (at least without a uke leash) and the sound is a bit Tin Pan Alley on occasion, which is great for that type of music, but doesn't work on everything I like to play. I would love to get a tenor but I don't care for the bowtie style, so that looks like it is out of the picture for me. But the Okamis are wonderful people and they make fantastic instruments.
I've never played a Koolau or Kelii so I can't speak to the attributes of those.
If someone asked me for a recommendation on what they should buy, I would tell them a KoAloha for the combination of the best sound and the best warranty. But if I had to run into a burning building and rescue only one of my ukes, it would be my Kamaka. That one has the sentimental attachment for me of not just being made in Hawaii, but BEING Hawaii. It is also the most comfortable for me to play, and everytime I hold it, or watch "Heart Strings" I feel like I have a tangible piece of the place I love. I may not be able to live there, or visit as frequently as I like, but with a Kamaka, you hold a piece of Hawaii in your hand.