Hi ehuesman,
“Creep” … or the tendency of any material to “relax” internally and become softer and deform with constant pressure over time … is inherent to many solid or polymer materials. It increases with temperature and as materials get closer to their melting point which is why it is more obvious in viscoelastic materials which change phase with heat and “flows” with pressure to some degree. Even concrete is subject to increased internal strain and creep with constant pressure over time. Foam creep is one of the reasons why a memory foam mattress with thick layers of memory foam can be risky regardless of the density of the memory foam.
“Indentations” are not as big an issue with memory foam as the softening of the material and the loss of its slow response properties without accompanying indentations. This is why many memory foam warranties can safely have a .75" warranty exclusion in terms of height loss because they would rarely tend to lose height beyond this point even if they become softer or lost their “memory foam like” qualities in the areas where they are the most stressed.
Because they work with their own mattresses every day … their assessment would be more accurate than anyone else’s but I would also bear in mind that comparing memory foam to latex is really an apples to oranges comparison and very subjective because latex responds primarily to pressure while memory foam responds to pressure, heat, humidity, and time (creep) so the variables that can result in how a material “feels” for any person or the “type” of softness that someone is most sensitive to and how time dependent their sense of softness may be can be very different. Each person may have a very different opinion of how a particular memory foam may compare to a certain ILD of latex so these would be “rough” comparisons.
Again … I would keep in mind that how a mattress or material feels is subjective and will vary by person depending on all the variables of how each material responds, environmental factors (more in the case of memory foam), and also on body weight, sleeping position, personal sensitivities to different properties of each foam, and the physiology and sensitivity of each person. I would also keep in mind that the two don’t have the same “ILD / IFD” (softness at 25% compression) even if on a subjective and more perceptual level they may have a similar “plushness” (however that may be defined). Even at the same level of “plushness” because of the phase change and sensitivity to heat of memory foam to different degrees … it would still be a more “in the mattress” and closely conforming or “surrounding” material than latex.
That would depend on many factors which you can read about in post #4 here and there is no easy or simple answer to this. Durability is relative to each person and also depends on the firmness and softness of a material and on many other factors and on the loss of a certain property which leads to a mattress becoming uncomfortable for someone or the loss of comfort and support. For one person the loss of “slow response” may be the determining “durability” factor while for another the loss of support that was marginal for them in the original design would put them over their line while for another one yet the loss of pressure relief could be the factor that leads to the need to replace a mattress. In practical terms … durability is not about the outright “failure” of a material (which rarely happens) but the gradual loss of certain properties that will affect the mattress as a whole in combination with all the other changes that are happening at the same time and at different rates.
In general terms … latex as a category is more durable (maintains its original properties) longer than memory foam but I don’t know of any statistical information that compares specific ILD’s of different types of latex to specific memory foams in terms of some specific definition of durability.
An example of how difficult durability comparisons can be is the use of thin quilting layers of say 1.5 lb polyfoam which by itself would normally be considered a less durable material (more subject to rapid softening). In an appropriate mattress construction though … the softening of a say 1" layer of 1.5 lb quilting polyfoam would have little effect on the properties of the mattress as a whole and could be part of a very durable design and construction for many people.
So having said that this is really not possible … if someone was over 200 lbs then I would begin to lean in the direction of avoiding the use of memory foam that was under 5 lbs and I would also tend to avoid latex ILD’s that were in the teens in most types of constructions or in thicker layers that are more likely to have a bigger effect on a mattress as a whole. The logical extrapolation of this based on my own “gut feel” is that latex in ILD’s in the teens would be less durable than most 5 lb memory foam in layers that were the same thickness and position in the mattress for most people and in designs where the thickness of the layer would have a significant effect on the feel and performance of the mattress as a whole. As much as that may seem like hedging … it’s probably as close as I could get to a meaningful durability comparison and even that may not be objectively accurate by some definitions of durability or in some circumstances.
I personally would place high value on the ability to exchange a layer in any circumstances where someone isn’t confident that their comfort choice may be the best one or when lack of the ability to test similar mattresses leads to the type of uncertainty where there was any worry or concern about the suitability of a choice. Of course each person may have a different personal value equation and a different balance or sense of importance concerning the tradeoff between risk and exchange options after a purchase. I personally would consider the lowered risk of a layer exchange option to be a significant part of the “value” of a mattress in these cases. The mattresses on their own site have more liberal and lower cost exchange options than their Amazon mattresses that also offer them but each one also has other tradeoffs involved in their choice (such as more limited or simplified comfort choices).
So overall … these are the types of questions that only each person can decide on for themselves based on their own comfort level with the risks and benefits of each of their choices and options. The only thing that someone else can really do is to help make sure they know the choices and tradeoffs they are facing and then get out of the way while they "weigh and measure’ each one by their own criteria.
FWIW … when I was making my own final choices between about 5 different “final options” … it took me weeks of hemming and hawing and getting down to smaller and smaller differences that in the larger picture probably weren’t all that important except in the context of somehow making a final choice and pulling the trigger. I think that any of my final choices would have been just fine … even though they would all have been different in some respects from each other. In other words … it wasn’t any easier for me to make final choices than it is for many other forum members here so I can certainly understand the process you are going through 
Phoenix