We still have our Sears Stackable units that were put in new in 1996. They are still working fine. Oops, I hope I didn't just jinx myself:S.
Being older they do have a larger tub than some of the new ones I have looked at but I haven't checked them all.
I have to respectfully disagree with the poster who said they don't work well. My clothes are spotless and come out of the dryer just fine.
For me having an on board washer & dryer, is not only the convenience, but I know the water temp and I know what had been in the washer. I also know the dryer temp. I love the fact that I can wash at my convenience. From a cost standpoint my w/d has paid for itself many, many times over.
BUT it is always a personal preference, plus we are fulltimers so we are in our Carriage 365 days a week. Hugs, Di