Metro Exodus' two DLCs very much build upon the base game. The two make for great short stories related to Metro Exodus, with their own tight focus. You'll definitely not find a lot of quantity here, but the quality is all there. I'll assume you have played Metro Exodus, if not, this review is probably not for you.
The Two Colonels are about Colonel Khlebnikov and Colonel Miller. Though, really, it's all about Khlebnikov, Kiril's father. The framing device is Colonel Miller tracing Khlebnikov's steps in the present time, while the flashbacks are where you play as Khlebnikov. This takes us back to the timeframe of the previous games, and as such, much of The Two Colonels is played underground.
There's definitely a strong sense of claustrophobia and atmosphere - closely recalling the earlier games in the series. If you weren't entirely sold on the open areas of Exodus, this will be a welcome return. Unlike Exodus, this DLC is very much a linear affair, and indeed, your path is marked out clearly. The focus here is on the tight spaces and encounters, rather than exploration. Khlebnikov's weapon of choice is the flamethrower, and indeed, the fire effects here are superb. Whether it be dangerous irradiated flora or fauna, there's a certain morbid satisfaction in the way they burn.
The Two Colonels has fantastic writing, as you'd expect from the Metro series. While tragedy and grimness is everywhere in the Metro series, The Two Colonels forms a rather pure dose of it. There's certainly some humour and atmosphere in some of the early celebration sequences inside the Metro, but things go to south pretty quickly.
Sam's Story takes us to Vladivostok, which is a breathtaking new location. Of course, we play as Sam, the only American in Artyom's group. After the events of Metro Exodus, Sam has just one goal - he wants to return to San Diego, his hometown. At Vladivostok, he meets another American (they could have named this The Two Americans, haha) who offers him a way out.
Sam's Story is structured much more like the Taiga sequence. There's an illusion of openness and freedom - and you can definitely go different ways - but the entire expansion has a strong linear flow. It's not quite open world, not quite corridor like The Two Colonels, but somewhere in between.
While The Two Colonels was devastating and tragic, Sam's Story has surprising moments of levity. There's a hilarious drinking sequence which I was definitely not expecting, but somehow fit in perfectly with the grim world of the Metro series. Captain Ed is a brilliant character too. The combat in The Two Colonels is much more like traditional Metro Exodus fare.
What makes Sam's Story stand apart is in the branching narrative and the very difficult decisions you have to make. Sure, Metro Exodus has multiple endings, based on how you play the game. But in Sam's Story, you get to make complete RPG-like decisions with huge consequences. These are exceptionally well done, and I have got to wonder - could the next Metro game be an RPG? Given the main struggle is over a submarine, the post-apocalyptic setting, and the choices offered, there's definitely strong Fallout 4: Far Harbor vibes here. I haven't yet played through the other ending, but I plan to do so when I play Metro Exodus again.
Both DLCs are welcome additions to Metro Exodus. If you liked the game, both are definitely worth playing through.