Bed mattresses are big decisions; it is perhaps the most important part of your house and it will last you for years on end. You must therefore be careful with such a decision and realize that there are many things most consumers over-look.
Firstly, and perhaps most importantly, you must understand what makes you comfortable. If you've slept on hard mattresses all your life, you may think that's what you like. Try the
ultra-soft pillow top, just to make sure. You may surprise yourself.
But do your research before you go shopping. Sleep over at a friend's house, take a look at the mattress when you go on a trip, do anything to avoid making the decision right in the store. No one wants to decide such an important thing while lying down in public with a salesperson breathing down your neck.
Keep in mind that mattresses are expensive because they should last a long time. Don't buy one merely because it's the cheapest you can find; you will be replacing it much sooner than you had to. You should expect to spend at least $500 on a good mattress. Anything less is suspect.
Size is the other key issue. Partnerships must decide on the bed together and must both know how much space they require and like. Look at the actual difference in inches between bed sizes. It helps to both know the number of inches AND to see the difference in person.
The key is to know what you like and what will make your body happy. Are a few hundred dollars either way really worth it in the long run? Don't be bullied into buying something that is not right for you!