Lara gains A real ally in Winter. The White Court is the weakest vampire court that we've seen.
Lara and harry have been attracted to one another for some time. I'm predicting that it's just physical and once they have a chance to exorcise the hormones they're going to realize that they'll never work long term. That doesn't mean they won't remain married, but it will be a sham. A political marriage only.
Harry gains protection from the White Council. Or, I should say, more protection from the White Council. Since they're a signatory of the accords, they couldn't just go and off the Winter Knight. Just as Molly still has the Doom of Damocles over her head, the White Council would be idiots to try and prosecute that given that she's now the Winter Lady.
Harry gains by access to the Raith Library.
Harry is protected from Raith trickery because Thomas is in the big house on Demonreach. Of course that still leaves Malvora, Skavis, and Barrowill trickery.
Lara might give in to her demon and feed on Harry, but my prediction is that she winds up feeding on the Winter Knight mantle. Which will bring her closer to Winter and possibly make her a suitable vessel for fae power. Better than Molly, as Lara has hundreds of years of existence in a court of predatory backstabbers. Mab is always five moves ahead in her three dimensional chess game.
This will also cause Harry to be further on the outs with the Svartalves.