We chartered a sailboat in the British Virgin Islands a couple of years ago and it came with one of each. None of our group, all in their 50s, had ever used a SUP before but we all picked it up very fast and the kayak was hardly ever used.
Safety, double kayak if you are actually planning on going anywhere once on the water. A person can go several miles easily in a kayak. If you just want to "run around the track" for exercise, then the SUP is great. A few rare souls will try to travel with and fish from an SUP and good for them. When the Powell winds com up, I'd rather be in a kayak because I'm down low and comfy and out of the water and I have a lot better chance to make a run for cover.
I prefer a SUP for so many reasons, not that a kayak is bad. First off my back doesn't hurt after an hour of paddling, unlike a kayak. Second, I get to see the world from 6 ft up....and it looks great. I love paddling at Powell as I can see down through the water so much better than a kayak. I get to stand on water...another plus. The negative is not as much packing room, however that is not what I am doing with my sup so it works for me. It is also a little more difficult to fish out from a balance and rod storage perspective, no doubt. It is a challenge to fish, however it is a riot getting pulled around by a big fish. Bottom line is they they both have their pros and cons however for me it is a SUP. Faster, lighter, more comfortable. Yes they take some time to adapt to, but what fun. Some would worry there will be a tidal wave/hurricane/tornado/flood etc and you will not be ready...maybe so however I am down in Baja right now and even in the ocean with waves and wind I prefer the SUP to a kayak. ( and I have been a river guide/boater for many years)
We have limited experience with both, but prefer the SUP.
One note|. Those kayaks are HEAVY when you are trying to lift them out of the water. This may factor into your decision. I could pick up and store a SUP by myself, with a kayak, it would take my husband and me
I just got back from Baja and took note of how the locals store fishing tackle and equipment on their boards. I know this is not a new thing for west coasters but I had not really seen it in action before. I have a Bote board with a tackle rack that holds my rods, a cooler and other things however for a board without that the locals had milk crates tied on with rod holders zip tied to the milk carton. Again not new, but new to me. It seemed to work really well, and very inexpensive.
Both kayaks and SUPs have their time to shine, but it seems like we have more of the times when SUPs shine than we have times for the kayak to shine these days. The SUPs are great if you just want to go out for an hour or two and paddle around. You can get pretty far going an hour each way, so the exploring is pretty good on the SUP. If I go much more than a couple of hours, my muscles are getting tired. Balancing on an SUP is a great core workout and you feel that after a while. I always feel more stable with a little knee bend as opposed to locked knees. That seems to take a toll on my quads after a while. I've ridden both inflatables and hard boards and have gone with all inflatables these days. If I were going to enter a race and seconds mattered, I would want a hard board. But they're a beast to carry and move. Besides, I have no plans to enter any races. The inflatables are great so long as you go with one that's 6 inches tall. There are ones out there that are 4 inches tall and they have a tendency to buckle in the middle if you have much more than a kid or a lighter woman on them.
For the kind of adventure where you go out for a half day or a full day and pack a lunch, a kayak is a good bet. You generally have a little more room to stow a lunch or some extra clothes. You can also just sit and talk without having to feel like you need to pay attention to balance. The two basic flavors of kayak are sit-in and sit-on. Sit-on seems to work best for Powell because you can get back aboard from the water if you tip over. It is a rare individual who can get aboard a sit-in from the water.
I happened to stop by Costco over the weekend. What should I see but the very items we're talking about, sitting side by side.
The $450 inflatable SUP looked like a pretty good one. The price isn't bad considering it includes a pump and a paddle. The $400 kayak looked more low-end and would probably offend a real kayak enthusiast, but had a low price and would surely suffice for the modest needs of lake water at Powell. In case the tags are hard to read, the kayak is a sit-on.
I can't comment on that particular SUP, but on a trip two years back, someone in our group spent $500 on a SUP from Sam's Club. To cut to the chase, it was not a good value as no one wanted to use it. Even at max PSI, it didn't offer enough support, and it was much more difficult to control than the one we own.
We have a C4 Waterman. It was more expensive, but it is very popular with those that use it.
I've been out on a friend's Costco Jimmy Styks SUP and it's not a bad board. It's better than some that cost a lot more. If an inflatable didn't have enough support, my guess is that it was a 4 inch thick board. I have no use for them except as a board for little kids.
The standout favorite SUP on our boat is a Solstice Bora Bora. It is the second board from the right in this picture.
The Bora Bora is a little over twelve feet long, but it has a streamlined narrow tip and tail that make it the fastest inflatable on our boat. The longer, narrower shape also gives it more stability and straighter tracking if you're moving forward. We have a Solstice Tonga (the far right in the picture above) that goes out as a second choice unless someone is much over 200 pounds or if it's going out with two people aboard. It has a lot of surface area, which keeps it high on the water. Here's a photo of how high the board sits in the water with my 180 pound son aboard.
And yes, he did get a talking to about going out without a life vest. As much as we like the Solstice boards, they are a little more money. I think they're a little under $600 on Amazon and that doesn't include a paddle. You also have to spring for your own bungee cord to stow gear on the front or back of the Solstice board because it doesn't come with that. As much as I like the Bora Bora board, you're pushing $650 by the time you buy a paddle and some bungee cord (and some heat shrink tubing to cover the knot in the bungee cord). For $450, the Costco special has much to like.
I have no experience with SUPs...yet, but received this SUP for Christmas from my in-laws and am looking forward to trying it out this summer.
I've had more experience with kayaks; mostly on the ocean (Alaska) for short sightseeing trips. My parents have an inflatable two person kayak that dissuaded me from considering inflatable SUPs. It doesn't track straight and is much tougher to move through the water than I would expect a similar sized solid hull to be, but hearing the good reviews on the inflatable SUPs here makes me wish I hadn't dismissed them since they'd probably be easier to store and haul around.