The choice between a plush mattress and a firm mattress is a matter of personal preference. Some people believe that a firm mattress is necessary for proper back support while you sleep, but that's no longer the case.
The inner-spring construction provides adequate back support on a mattress, which has nothing to do with how plush or firm the mattress is.
Lie down on the mattress and try to roll over. If it's difficult to do, the mattress is too soft. If you lie on your back and can reach your hand underneath the small of your back, the mattress is too firm.
Enjoy adequate support when you buy a mattress with the appropriate number of coils. A king-size mattress should have at least 450 coils; a queen-size mattress requires 375 coils; and a full-size mattress should have 300 coils.
The padding on top of your mattress should consist of soft foam, which holds its shape better than polyester batting.
Make Yourself Comfortable
In the store, lie on the mattress for at least 15 minutes before you buy it to determine which mattress you like best.