Hi ikoz56,
A thicker mattress will have a greater range of compression from soft to firm (it doesn’t “firm up” as quickly) and can adapt to the shape of the body a little better. All other things being equal … a thinner mattress will tend to feel firmer than a thicker mattress. There is more about the effects of thickness in post #14 here. More layers also provide more options to customize the mattress either before or after a purchase.
You can use the testing guidelines in the tutorial post to test for PPP (Posture and alignment, Pressure relief, and Personal preferences).
With your lighter weight the odds are higher that a thinner mattress may work for you but with your husbands higher weight he may need or prefer a thicker mattress. There is more in the first part of post #2 here about couples that may have have different needs and preferences because of differences in weight, body type, or sleeping positions.
Phoenix