The problem is that a lot of expensive phones do not have better security. Except for a notable few, security tends to be fairly shoddy accross the board.
Very few manufacturers have decent and guaranteed update schemes.
This is where my experience differs. The cheap phone manufacturers have a lax view towards security. A lot of R&D time goes into making devices secure and even more R&D goes into cracking that security. Security isn't generally a priority for cheap and nasty phones, which often makes retrieving data from them a trivial task. Sometimes even to the point where the passcode is there for show rather than an actual security measure.
Apple is one example where an expensive phone isn't necessarily secure, but they do implement some elements of their design in a secure way.
Cheaper phones also tend to have larger batteries and do longer with those batteries
Can you provide some examples? My phone has a 3000mAh battery and generally get about 2 days of usage out of it before requiring a charge.
There's no evidence to support the notion that cheaper phones wouldn't have equally sound connectivity and manufacturers pushing the edge on high end form factors often means a bigger chance of something going wrong there. It's harder to stuff a proper antenna in the tiniest housing possible.
Are you just making things up now? To the contrary, you'll find the higher end phones do have better connectivity. My phone will support up to LTE-A Cat 16, which has a maxmium downstream rate of 1 Gbps. The newest phones are now coming out with support for Cat 18 and above (1.2 Gbps downstream). You might ask are the telcos geared up for that sort of thing? You bet they are! (At least in some parts of the world). The Samsung Galaxy S8 one of the thinnest phones out there, has also been recommended for rural coverage in Australia due to the higher gain internal antenna, something very few phones are capable of.
It sounds like you've fallen into the "it's more expensive so it's better" trap. Of course people want to believe that when they spend an arm and a leg on something. High end phones tend to push the envelope in regards to performance and that means they usually run hotter, are less frugal, have more issues with less proven construction techniques, are more fragile when it comes to drops et cetera. If you want something that just works you buy technology that's further down the curve without ending up at the cheap end. You could even buy a phone and a spare in case something happens for less than the price of a single high end phone.
Again, quite the contrary. I did my homework, researched phones which met my needs then went out and looked for the cheapest possible price I could buy that phone for. I didn't just blindly pick a Samsung because I'm some kind of fan boy (in fact, this is the first Samsung phone I've ever owned). Yes it's more fragile than my previous handsets, but a case fixed that. As for running hot, again, are you making things up again? Almost all smart phones will run at elevated temperatures when pushed, even the cheap and nasty ones. During normal usage, heat isn't noticeable.
I'm not saying high end phones are without merits, but they haven't done better in regards to the basics for years now. That was true about a decade ago, but those days have long gone.
It sounds like you've written them off without actually knowing a lot about them. I work with phones and mobile devices every single day. I spend a lot of time working in R&D and working on security aspects of the devices, that's my day job. I won't pretend to know every model of phone inside-out but I have a fair idea.
Security aside for a moment, if you can find me a reliable, cheap Android phone with a Cat 16 or higher modem, has a long-lasting internal battery, that supports the 700, 1800 and 2100 MHz bands, running the latest version of Android, I'll certainly take a look.