Hi amy0901,
While I can’t tell you which mattress to choose because each person (or parent) may have different preferences and criteria that are important to them (see mattress firmness/comfort levels in post #2 here) … I may be able to help with “how” to choose the mattress that you are most comfortable purchasing for your daughter (and for your guests).
The first step would be to decide on the materials you are most comfortable with and post #2 here may be helpful with that part of your choice. I would tend to avoid memory foam for children (partly because of potential sensitivity issues and partly because it can be too soft for children).
Post #2 here includes links to the better forum posts and topics about mattresses and children that should give you some useful information and guidelines and should also be helpful. They also include links to many different options that would be suitable for a child (and would be inside your budget) including several that you mentioned.
Both of these come in a wide range of firmness options so which one was softer would depend on the specific firmness level you choose. Either one could be softer or firmer than the other.
I would keep in mind that your daughter will be growing and developing and her needs and preferences may be very different in 10 years than they are now. Most children do best with a mattress that is in the firmer range but as they grow and their body develops they may need some additional softness in the comfort layer to help with pressure relief (depending on their body type and sleeping positions). If you are looking at a component mattress I would tend to look at thinner mattresses initially (such as two 3" layers) which will be fine for her now and then add a topper when and if she needs it. If you are looking at finished mattresses then I would tend to choose something in the “medium firm” range (which isn’t an exact firmness rating but most manufacturers would know which of their options would be suitable for a child).
It may also be worth choosing a firmer mattress and a separate topper so that your daughter can sleep on a mattress that is firmer and your guests that prefer a softer sleeping surface can add the topper.
The better options or possibilities I’m aware of in the Richmond, VA area are listed in post #5 here.
All of the options you are considering would make a good choice and don’t have any weak links in their design or materials so when you are down to finalists that are choices between “good and good” and there are no clear winners between them then your final choice (see post #2 here) will really depend on which one is the best “match” for all the objective, subjective, and intangible parts of your personal value equation that are most important to you … but only you can decide which one is “best for you” because any of them would make a suitable choice for your daughter.
Phoenix