A priori, the reasoning is simple. If it's newer and more expensive, it has to be better. Usually it is. But not always, and there are few cases in which we find that a previous mobile has turned out to be better than a more recent mobile, and therefore, more expensive. And it is that sometimes the most recent or the most expensive mobile is not always better.
Contrary to logic
The big problem is that identifying the newer and more expensive mobiles that are worse than the previous models of those same mobiles is not something simple, it is not even logical. That is, if you ask me if it is better to buy the Sony Xperia Z3 or the Sony Xperia Z5, I would tell you that it is best to buy the latter, as long as money is not a determining factor in your case. I would tell you that as a logical reasoning, without having investigated each of these motives well. I know above all the technical characteristics of both smartphones, and I take it for granted that the new generation is better than the previous one, which is true. But it is also true that, for example, the new Sony Xperia Z5 right now have a stability problem that the Sony Xperia Z3 does not have. And that could be decisive for a user looking for a mobile that is stable and works well, and not a mobile with the latest technology and with some stability. For example, some users of the Sony Xperia Z5 Compact, claim that it is slow when capturing photos, more than the Sony Xperia Z3 Compact. Which one is better to buy, therefore, if you are interested in having a small format mobile with good photos?
I already told you that the Sony Xperia Z5 Compact is a better mobile, and those stability problems will be solved, but it is also true that the Sony Xperia Z3 Compact is cheaper.
It depends a lot on the mobile
The worst thing about all this is that we cannot generalize. We cannot say that buying an older model is more advisable in all cases, or in certain cases in which the same circumstances occur. We cannot establish a pattern, and therefore, choosing between one model or another of mobile will require a research task, looking for comments about other users on the two smartphones, comparing prices in different stores, evaluating the different characteristics of one or the other. , etc. But buying the latest mobile is not always buying the best.
On the subject of slowness in the z5, when taking pictures, it is not the fault of the camera or the mobile. Most of them are to instantly synchronize the download to the Internet, cloud, etc ,, the users observed better their configurations, they would make better use of the mobile, I am and have been a user of the entire xperia range and I opted for this brand because they are phones mostly Samsung with Sony caps and Sony photography etc imaging technology and 70% more resistant than any other brand design. It is ugly perhaps but safe.