Arden
Blackwing Lair Raider
Having recently seen the first two seasons of Slow Horses and the whole five seasons of The Bureau, I would say both shows are good but very different in tone and scope. Slow Horses is written with some caricatural characters while The Bureau leans toward a more subdued approach, trying to keep a veneer of serious and realist spycraft (a veneer that breaks here and there, but is mostly well maintained) rather than one of fun spy fiction. Fun spy fictions are fun, so I am looking forward to this 3rd season of Slow Horses.
That's a fair summary of how they are different. Would still say The Bureau was just better though- better writing, directing, story, acting (with the exception of Gary Oldman, who is the best actor in either show imo). Might be because I prefer gritty and realistic to pulpy.
Again though, I still like Horses a lot. Enjoying the third season- though I'm getting pretty sick of everyone using River as a punching bag and him taking it like he deserves it.