Hi Ket2593,
It would depend on the specifics of each mattress you were comparing but post #2 here has more information about the differences between a latex/polyfoam hybrid and an all latex mattress.
You can read a little more about the different types of latex in this article and in post #6 here and there is more about the differences in how they “feel” in post #7 here but it would be best to test each one in person to see which type of latex you prefer. Both are great materials.
The problem with the pillowtops that soften, cave in, or indent within months is not so much the pillowtop style of construction itself (which is like a topper that is attached to the mattress) but the quality of the materials inside the pillowtop and the upper layers of the mattress. Most of the mainstream pillowtop mattresses use fairly thick layers of lower quality soft polyfoam in the pillowtop which will soften and break down much more quickly than higher quality/density polyfoam, higher density memory foam, or latex. In other words … it’s the quality of the materials in the pillowtop that are more important than the pillowtop type of construction itself. This is true for all mattresses regardless of whether they are a pillowtop or not and you could have a mattress that was just as thick as a pillowtop except the layers were all inside a single cover instead of having a separate pilowtop attached and if there was too much lower quality foam in the upper layers you would still have the same problem even though the mattress wasn’t a pillowtop.
A mattress that uses either latex … higher density memory foam, or higher density polyfoam in the comfort layers would have much less chance of softening or breaking down prematurely than lower quality materials regardless of the type of construction.
Phoenix