Hi polmattress.
Welcome to our Mattress Forum. 
It sounds like you may be suffering from a little bit of “analysis paralysis” and you’re definitely not the first (or last!)
Following the steps in the mattress shopping tutorial one at a time without missing any is the best way to avoid this.
With higher BMIs and a weight differential between you and your husband, the Mattress Durability Guidelines will be especially important. Mattresses with coils are both comfortable and supportive for heavier sleepers, and many will say they find them more durable than beds constructed solely out of foam. This, again, comes down to making sure you choose the appropriate materials and overall thickness for your sleeping profiles and BMIs. There are also a number of forum posts and threads about mattresses and higher weights and a forum title search on heavy (you can just click this) will bring up many of them. Some examples include post #2 here and post #2 here and this thread.
With regards to the Presto…Latex is the most durable material of all types of foams but some sagging can occur for softer (lower ILD) layers when said comfort layer is too soft for higher BMI ranges, (unless - and this is very uncommon - there is a defective batch of latex. I wouldn’t discard the Presto based on reviews, as your experience and configuration will be entirely unique.
Talalay and Dunlop do differ in feel. It has been described in the forum before as the difference between angel food cake (Talalay) and pound cake (Dunlop). Talalay latex is the most popular as a comfort layer because it can be made softer than Dunlop and is more consistent in its softness across the entire surface of the mattress. Dunlop however is also used in the comfort layers because of its firmer and less “lively” nature which is attractive to some who prefer its feel.
If you enjoy the traditional innerspring feel, then a hybrid is a great compromise! Hybrids maintain the “bounce” associated with an innerspring mattress, and are slightly cooler as there is more air flowing through the coils (as opposed to no air flowing through an all foam mattress).
Going back to my comment about the weight differential - it is my guess that you have fairly different needs with regards to support and comfort on a mattress. You may be interested in checking out split configurations.
I would suggest checking these options out…
Arizona Premium
Sleep EZ
FloBeds
Latex Mattress Factory
Nest Bedding
They, like Memory Foam Comfort, are Trusted Members on our forum which means we thinking very highly of them and believe they compete with among the best in the industry in terms of quality and knowledge.
MFC offers great products and they are very knowledgable. If you are still interested in the the Presto, I would suggest reaching out to them directly with your concerns, sleep stats, and any other information that may be pertinent for them to know and see how they can best guide you.
And not to sound like a broken record, but regardless of which mattress you ultimately select, I’d make sure to have a detailed conversation with your finalist retailer/manufacturer and provide them with your stats, body type, sleeping styles, general preferences and history, some general information about your current mattress, or what you have tested, and any other specific information or circumstances that could affect your choice of a mattress.
I hope I’ve provided useful information here. Please let us know if you have more questions!
NikkiTMU