I'd contrast them this way: Vaults of Terra is a more "conventional" Inquisition adventure whereas The Horusian Wars, on the whole, are more "experimental".
The way each author approaches worldbuilding, character development, plot, twists etc is almost fundamentally opposed.
For example: If you read The Carrion Throne, you'll get the entire package deal of world, cast and plot basically gift-wrapped in an exceedingly pleasing, if not earthshattering, package. With Resurrection, you'll get something less complete, albeit fascinating. There are many glimpses of revelations, character moments and worldbuilding, but - at least to me - few of them felt fully realized to the extent where I'd call it close to on par with The Carrion Throne as an individual offering.
Wraight has short stories for Vaults that support the books (including the excellent Interrogation of Salvor Lermentov!), they aren't really essential reading. Their exposition and added character work complement the novels, but can also be enjoyed on their own - and if you miss them, you're not going to miss much in the wider context.
French, meanwhile, builds crucial aspects into the short stories, foundational character development, world building and so forth. Not reading them will, in my opinion and experience, seriously diminish what you'll get out of Resurrection and Incarnation. Where Vaults are a simple package deal, John externalized a lot of the legwork into the short stories that were released sprinkled around the books, some before, some after Resurrection, some since Incarnation. Divination, as such, is a fundamental anthology that can't be left out without effectively hamstringing your enjoyment of what John is going for with the trilogy.
I'm torn on the approach even still. It certainly allows a great deal of experimentation, both narratively and stylistically, and it trims fat from the novels. But it also creates dependencies that will not be immediately apparent to the reader, especially newcomers or those who only buy print and thus had to wait nearly 3 years on Divination, as the third released book while the preceding two kind of expect you to know various things from the included shorts. It's a shortcut that doesn't necessarily work with BL's publishing model and schedule, whereas - to pick up the comparison to Fehervari - the Dark Coil uses each story as an additional piece in the wider puzzle but does not require or expect you to pick them all up just to get satisfaction out of any given piece you may pick up - especially the novels.
With the Coil, you can bounce back and forth as you please - although obviously, some story links click more easily in certain directions, or the second time around - whereas with Resurrection, it can feel like a chore with very distant characters you're asked to care about with little basis, as the basis itself isn't part of the ongoing narrative but was instead released some weeks or months before the original hardcover release as a digital-only short story on BL's store.
To wrap back around, looking at it from this angle, the Vaults of Terra quite simply win based on being hugely more accessible to begin with. Their appeal is more self-contained, the narratives follow more traditional curves and the books let you into the characters' heads far more easily. With The Horusian Wars, there's more of a deliberate distance between the reader and (certain) characters that can be hard to get behind, especially without the external pieces. Whereas Vaults is - for all its whacky aspects - a more mundane series, The Horusian Wars are quite arcane, more esoteric.
On more than one occasion, I also felt a difference between the way The Carrion Throne and Resurrection "hide" information from the reader. With The Carrion Throne, certain reveals and twists are part of the dramatic arc, with hints and foreshadowing, or nudges to the lore for the invested fan. Getting the truth out of the cast and events is part of the investigation. With Resurrection, there were numerous instances where information was conveyed to characters, but not necessarily the reader. Where the characters were in the know, but didn't let the reader catch up with what they knew. Where scenes would sometimes end rather dramatically or abruptly, just before things would need to be spelled out. That led to somewhat of a disconnect between me, as the reader, and the characters within the story that I was expected to root for. Instead of figuring things out alongside the Inquisitor and his retinue, I was made aware of the Inquisitor having a much better grasp on things than he let on to me, while thinking I myself was left with deliberately incomplete, or nebulous, information.
On top of it all, I think that The Horusian Wars are generally catered more towards hardcore fans who have been following the setting for a long time and are more than passingly familiar with its intricacies. References to obscure lore are a dime a dozen. Certain elements exist that have been debated, or even retconned, generations ago and may seem like they come out of left field within the narratives. With The Carrion Throne, by comparison, while it does take some lore references as a core component of its narrative, something for fans in the know to look forward to, it gives the reader enough on those things to keep them in touch rather than close the book and go wiki things up.
While both trilogies obviously have wider stakes in play, and are heating up for big climactic third parts, I believe John French is gambling for the higher, bigger-scale payoff or revelation than Wraight is. Chris seems more content with painting in gaps in the setting, exploring seldom-trod roads and doing so via cracking narratives that allow him to look behind the curtain and delve into the seedy underbelly of Terra, French probably has the potentially more impactful series on his hands, for the setting as a whole, with more moving parts that could influence the setting going forward. His narratives are deliberately constructed within the spectrum of his plans and will most likely require full reading of the series for a real payoff, I'd say, whereas Wraight's books, despite overreaching aspects and most assuredly some big reveals in book three, seem more concerned with telling a compelling, enjoyable, intriguing story in the moment, in the book you're holding by itself.
And... then there's the obvious difference in prose styles. Wraight is more straightforward, accessible (again) and clear, whereas John French can get very... flowery, esoteric and sometimes convoluted. His style here is fitting perfectly to what he's doing, but it can also make the trip harder to get through, as the complexities of the narrative itself and the prose can easily have a cumulative effect to slow you down or even confuse you in some scenes..
Edited by DarkChaplain, 26 June 2020 - 10:15 AM.