This is a hard question to answer due to the many different types and levels each one produces. Unless you pick out a particular mattress from each manufacturer to use as a comparison there is no way to judge them apples to apples. Are we talking innerspring or foam? Latex mattress or memory foam mattress? Firm or pillow top?
As you can see it would be very hard to say that Sealy is better than Simmons or Serta is better than Sealy without knowing the exact mattress in question. It is not like comparing Tempurpedic who only makes visco memory foam mattresses or Select Comfort with the Sleep Number bed.
Since all three make traditional inner spring along with latex foam and memory foam mattresses I will address the regular spring mattress right now and save the foam beds for another article.
Sealy Posturepedic was created by doctors to be the perfect mattress way back when. With the advancement of all mattress makers it would be hard to call anyone the perfect mattress. The Posturepedic innerspring mattress is one coil unit acting together to provide total body support with layers of various types of foam on top for comfort.
Sealy makes great durable mattresses and always have. By the way Sealy got their name from the town they were originally made and first produced an all cotton mattress long before “organic natural” was a buzz word.
Serta makes the “Perfect Sleeper” among others in their line-up. If you recall Serta advertises with the Serta Sheep and claim to make the worlds most comfortable mattress. Again, this is a wild claim as every mattress is as different as every body that sleeps on it.
Serta makes durable innerspring mattresses that last over the long haul assuming you did not buy their budget line which may not last as long. Serta is owned by a group of mattress manufactures who all banded together to form the Serta mattress corporation.
Simmons is the unique one of this bunch as they specialized in individual coils instead of the traditional continues coil unit favored by the others. To me this gives a big edge to Simmons mattress and their Beautyrest line.
If you had one mattress from all three in front of you and the salesperson told you that one would reduce or eliminate all movement in the mattress so that your partner would not wake you by moving around you would most likely choose that one.
That is the advantage Simmons mattress has over the others. Who does not want less partner disturbance if they can get with all other things being equal.
Serta or Simmons or Sealy
Claiming either Serta, Simmons or Sealy is the better mattress is almost impossible from a general sense. I do think overall Simmons mattress has the advantage with the type of coils they use but that does not make them better than Sealy or Serta. It comes down to what feels best to you.
And for those that wonder if you need to spend $3000 on a innerspring mattress to get quality and a good nights sleep the answer is usually no. A less expensive mattress will do just as well but not last as long as the more expensive mattress. But do yourself a favor and do not go for the cheapest mattress as that will be nothing but trouble.