I have had the Kitchen Aid KEMS308S for 5 years. I had not noticed that the microwave power was low. I doubt that power will be an issue. I assume that many ovens have cool down features. They are not running when the door is open. It is ture that the fan makes some noise, but it isn't that noticable. When I originally purchased this oven I had been intending to get individual ovens, but it turned out that the individual ovens had been discontinued. I see no difference between your choices because they are all double ovens and when one fails, they both fail wheras individual ovens could be replaced individually. I have not heard of the microwave section showing a high rate of failure. You didn't even mention the advantage of the micro/convection. It is not just a microwave, but a real convection oven with a broiling (sort of) element. It is not a speed oven because it does not microwave and heat at the same time. Actually it CAN microwave and crisp via the broil element. Anyway it is a small second oven that can bake a pie or bread (or a small trey of cookies I suppose). It heats far faster than the regular large convection oven because it is small. I find it very useful. The only problem is it is occasionally in use when I would want to reheat a cup of coffee etc. I keep an old microwave in the garage for those cases. While I hope I have relieved your concerns, I believe that there IS an issue. I have had no problem with my oven, and it has been several years since the Main contingent of problems: similar models have encountered a higher than normal thermal fuse blowing during the large oven self cleaning cycle. Unfortunately, the fuse is located on the back of the oven and is a $50 item and shuts everything down. Of course, most people see no problem (myself included) and the problem is certainly due to excessive heat behind the cabinet that could probably relieved by making sure that there is a little more open space back there since you are still installing cabinets? In any case, this is probably a general issue. Other ovens have failed on self clean cycles. At this point, many people concider the self clean to be a marketing ploy and don't use it. Perhaps we just don't make enough spattering roasts, but I have easily wiped down the main oven. It wasn't stuck on hard. Perhaps the surface has anti stick coating? My self cleans have been done mainly to test the thermal fuse problem. By the way, the microwave interior is stainless steel and IS much harder to clean. In fact, that last sentence is probably my most important piece of information. I imagine it would apply to other convection microwaves.

We installed a Miele Speedoven in 2012 and have no regrets. It is in a wall cabinet at counter height and is used all the time. It heats up very fast for baking allowing us not to use our 36" oven when not needed. It microwaves, bakes, and broils with all types of combinations of those heating choices. The drawbacks are the price and you need a 220v line to power it. The quality is excellent and have not seen another oven that can do what this does.

The convection steam oven can be used just like a normal convection oven though it heats up much quicker. With our family of four we use it the most of all the oven's (have a 30" Wolf below it and a 36" BS range). Almost anything we do for a dinner can be done in the steam oven rather than heating up and dirtying one of the larger ovens. It roasts meat and chickens the best of any oven using convection humid mode. Bakes bread excellent except for high heat baking (only goes to 445), use it for cookies, dutch/german pancakes, makes an excellent crust on any food. Don't get caught up in the 'steamed food' mindset, it's all convection oven when you want it to be. We do use the steam mode for veggies (we'll never micro them again), sometimes fish, though I do prefer fish baked or fried. It makes excellent rice and I've even done pasta in it (though not as handy as I like checking pasta in a pan for perfect doneness). It's the only way we make rice now. I've made custards in it, works great, no water bath. Reheating food is great, again no more micro for that. There are a lot of modes that make food more convenient to prepare. My DW likes to make hard boiled eggs in it (obviously not boiled), she just leaves them in the paper carton and steams them, got to be careful taking them out if not on a cookie sheet as the paper gets pretty limp. I made brown sugar (turbinado) bacon in it last weekend and it turned out awesome, nice and crisp in about 25 minutes. Like I mentioned we use it a LOT. It's a bit pricey for a rice cooker, or a micro replacement but for all the other things it does I would lose my 30" Wolf over the steam oven anyday of the week. For me the only limitation is the heat range as max is 445 but I do make cast iron pan pizza in it and it turns out wonderful. For normal pizza I crank the BS to 'beyond' 500, some breads want a higher heat. It doesn't have a broiler so having at least one oven with one works great. I have the Wolf CSO so do fill the water reservoir manually but that's maybe twice a week at the most and takes all of a minute. We've had ours over 2 years and still haven't used it to it's full potential. Once you get it you'll understand how great it is, it will inspire you to cook differently and more conveniently with better results over a std oven or microwave. IMO there s/b one in every kitchen, it's more of a workhorse than any other appliance.

I love the huge oven cavity that my Bluestar 30" has ... and I honestly have a need for that large cavity once every few years. It's one of those "when you need it, you really need" it things. But that need doesn't happen all that often. In our current remodel, we are getting a Miele CSO and a Miele Speedoven; those are only 24" wide. I expect that, like everybody else in this forum, I'll use them much more frequently than the big oven. If you never cook for really large groups of people, I could definitely see you be OK with smaller ovens. And from what I can tell, it's not as if a 30" wall oven was small. I do have to caution you though that it doesn't look as if the Samsung oven is an actual combination-steam-oven. Instead, it looks to me as if it is a regular oven that has a steam injection feature. That's a lot more limiting. Please read up on the difference before making a decision. Also, while I don't know anything else about this particular model, this forum is generally somewhat negative on Samsung appliances. They don't really have a great reputation for reliability right now. I wouldn't know whether that applies to their ovens, though, or if it is just their refrigerators that everybody seems to hate on.