Only the XA 2plus 64 GB internal storage variant.
Also bigger screen (but ultra has it too) and slightly better screen to body ratio.
GSMArena reviews rated the XA2 series as overpriced at used hardware.

Do we really need 6GB RAM on the phone? I have a phone with 1.5 and a tablet with 4 and it's the same thing in most cases. Android doesn't do multitasking so the only noticeable difference is when starting something demanding and huge. But part of that also lies on way faster SOC on tablet and not just the fact that app is frozen in the background.
And for sailfish............ well, there's not enough app to fill that RAM anyway

That's what we thought (were told) when Jolla came out with 1GB. Within less than a year since the release an update came out that could not handle more than 3 very basic applications running simultaneously.

Yes, qt itself has somewhat a large memory footprint so some extra is never a bad idea.

It really depends. I would say that for "normal" smartphone usage in 2018 2-3 GB RAM should be enough, especially if applications are reasonably optimized (eq. drop non-critical resources when they loose focus, etc.).

On the other hand our phones are more or less notebooks a few years back performance wise, so it might make sense to use them the same way, either when fooling around as a developer/it enthusiast or when the phone no longer works as a mobile device but rather like a static one (say a device with smashed screen or bad battery acting as a lightweight server).

In such cases it could be RAM rather than the CPU or permanent storage acting as a bottleneck. For a few not-really-mobile-but-interesting use cases that might be RAM intensive:

• emulation (old consoles, dosbox, wine, Android, etc.)
• virtualization (at least some 64 bit ARM CPUs should have extensions for hardware assisted virtualization)
• running containers & flatpacks (better app availability, running desktop apps)
• compiling non trivial stuff on device
• running advanced navigation and NLP algorithms on device (OSM Scout Server often hits memory limitations on Jolla 1 and other low RAM devices)
• running local advanced speech recognition and speech synthesis (eq. not running potentially sensitive data through public cloud)
• running some basic AI and machine learning tools & data analysis (as above & could be actually quite useful on mobile devices)
• more RAM means more stuff can be cached from permanent storage, possibly leading to faster app startup and better responsiveness
• running non optimized desktop apps (could be the only option for specialized apps)
• running an absurd amount of apps at once (sadly, not all apps start fast and properly keep their state when re-started, so just keeping them running can be more convenient)

So even if it might seem absurd, I say more RAM can't hurt, as long as there are not critical downsides of that, such as very bad power consumption or all devices being too expensive due to excessive amount of RAM.

Well, somewhat good news is that Sony Xperia XA2 (pioneer) is supported by LineageOS 15.1
https://download.lineageos.org/pioneer

@acrux How that can be good news? Lineage s-h-i-t is anyways android so I don't get it. Sure Lineage is better than stock androids like less spying etc. But it's Still power hungry, unstable and evil operating system.

One man's "evil" is another's "usable".

A mobile phone is primarily a communication device. What good is one with a "nice" operating system that you cannot use for that basic purpose? That is the real reason people still flock to "evil" operating systems: the availability of communication solutions (as well as other "apps").

Trying to answer:
1. You have more choice: stock android; sailfishos; lineageos; some other rom thanks to Sony open device program...
2. What's wrong with Android? Yes, it is almost dominating the mobile world, but we should be thankful to Google releasing it's source code through aosp. This makes LineageOS and other rom's possible. In fact - LineageOS is fully open source (except vendor firmware&drivers). We can't say that about SailfishOS (using the same vendor firmware&drivers through libhybris + closed bits in SailfishOS itself). We may go even further and say that SailfishOS on real hardware would not existed if there did not exist Android
3. To my experience LineageOS is very good on my Nexus 6. I have not installed any Google Apps package to it and using only open source software repository F-Droid. It has been very stable through all the weekly builds. I do not remember any need to restart it except these weekly upgrades. As of power hungriness - my December 2015 Nexus 6 lasts longer than December 2017 XperiaX at my usage pattern. Well - if with Gapps, then it could be vice-versa... As of evilness - Android is controlled by US and SailfishOS by Russia :P I do not remember a case through history that US has tried to conquer and occupy Finland (or Estonia)...
4. Best greetings to the other side of Gulf of Finland

IIRC, bits of Linage OS are used by Sailfish OS/libhybris to provide hardware adaptation/android drivers for a device. So Lineage OS supporting a device means it is more likely to be supported in the future by both community ports and official Sailfish OS releases.

(Porters please correct me if I'm not remembering things right. )