Hi zacharybloch,
I switched your post into a new topic of it’s own since you are in a different country than the member that posted the original topic.
It would depend on the specific mattresses you were comparing. Both types of mattresses come in a very wide range of prices and some memory foam mattresses would be more costly than some spring mattresses and vice versa.
While I can certainly help with “how” to choose … I don’t make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
Assuming that the materials in a mattress you are considering are durable enough for your body type and meet the quality/durability guidelines here relative to your weight range … the choice between different types and combinations of materials and components or different types of mattresses are more of a preference and a budget choice than a “better/worse” choice (see this article). The best way to know which types of materials or mattresses you tend to prefer will be based on your own careful testing or your own personal experience.
Unfortunately … I don’t have any particular knowledge about the Australian market so I won’t be able to help much in terms of specific retailers or manufacturers I’m aware of there but the steps involved in choosing a mattress would be the same and the mattress materials that are used in Australia would generally be the same as the materials in North America. I would also read post #2 here (except replace “Israel” with “Australia”).
Post #2 here also includes links to most of the forum topics from Australia and post #7 here includes a list of many Australian manufacturers and retailers and a few comments about some of them as well that will hopefully be helpful as well.
Phoenix