I am also looking to get some lighter wheels for my Ripley LS this spring, however, I've been shooting more for the 1300g range. My aggressive weight goal makes the Hydra tough sell.
Overall, I've been comparing a number of hubs, and what I think it comes down to is that DT has a small and light free hub engagement system. By all reports it is durable, but the small diameter of the Ratchet Drive means you can only put so many teeth in it and maintain that durability.
The I9 on the other hand has a big engagement ring with many tiny teeth and 4 pauls to engage with them, and that all adds weight. Generally, across the range of high-end hubs, the high-engagement hubs are heavier and the lightweight hubs have less engagement. There's no way around that, you have to pick which is more important to you.
If you have Ibis branded hubs right now, the DT have the same number of engagement points, so you won't miss it, FWIW.
I had some King hubs back in the day, and going from 18t to 72t back then, it was obvious how important high engagement is for my style of riding. I say riding style is important because situations like technical climbs or terrain with a lot of corners you have to accelerate out of or short steep climbs, the extra engagement is really valuable. Descending and flow trails, not so much. Currently I have a bontrager Kovee wheelset with 108t and the Ibis 938 with 36t. Honestly, I don't notice it much, because I typically choose the lighter bontrager wheels (with lighter tires too) for rides with more climbing and tight corners, and the Ibis wheels for more descending and rougher trails.