Okay, now I have time to answer this properly.
The last three updates were probably some of the better ones. I can tell this encounter was planned well in advance. The placement in the overall plot feels a bit random, but the content does not leave cause to complain.
Also, I am a sucker for what-if scenarios and facing the alternate version of main characters.
Also also, I find that I like the originals better (i.e. Eva and Rico as opposed to Priscilla). From the designs, to personalities, to magic phrases. Never got into the mind meld stuff. I just have to wonder what kind of quest it would have been in their alt-verse.
I kinda drifted away a little when the quest got overly mechanical (six digit numbers do not make for intuitive rules), but that got me to de-lurk just to say it. You've done a good job with them, Naron.
For one, I find it easier to streamline actions when combat is happening because I know no one can go on long tangents. It is a thing and I would be inclined to agree that those last Updates have ended up quite well.
However, I also think the main reason they shine is that they are much faster paced and thus stand out among the slower, more social-attuned 'normal' Updates. Plus, having battles every second Update or so would get boring really quick.
Leaving your and my opinions on who is better aside, I can see why the alternative forms may be more appealing. Personally, I usually try to go for the more interesting options instead of what might be better; a single soul living in two bodies is a concept I have rarely seen, so I went for it once I had already decided on what particular magic the twins would have. It is hard to pull off and even more difficult to do well, but I am happy with Priscilla as she is.
The rest of their differences... well, as I said, the Benign twins were made much later than the Primordial twins (wordplay unintentonal). If I could remake the latter from scratch right now, I would change
a lot about them... but this is kind of the thing: I can not. I dug this grave, so I will have to lie in it until the epilogue is written.
Anyway, thank you for the critcism, positive and negative.