We have a King sized memory foam mattress in the house. I'm about ready to throw it out the front door! Worst mattress I've ever had to sleep on. The memory foam is too soft and very uncomfortable for me with my neck and back (Then again, I have neck and lower back problems). It's so soft that I have a hard time just rolling over on the darned thing! Also, I find the foam to be very warm to sleep on, as if the foam is acting like foam insulation and reflecting your body heat back to you. DW on the other hand likes the mattress.
In the MH, we have a Queen sized innerspring pillow top mattress. Just soft enough on top but firm support which is much better on my back and neck. By far, one of the most comfortable mattresses I've slept on.
Whichever you choose, it would be my recommendation that you don't go too soft. Then again, everyone is different.