Legends, Sky 1 / The Strain, Watch

Let's face it, there are so many big-budget, densely plotted US TV imports around now that it seems a little hackneyed to compare them to buses - but even by those standards, scheduling the two newest ones concurrently seems a little careless. Your choice: Legends, an FBI procedural with a twist from Homeland show-runner Howard Gordon; or Guillermo del Toro's vampire virus horror The Strain.

Neither premise is particularly original but Legends (***), with Sean Bean in the lead role as veteran FBI agent Martin Odum, stands out as an audacious tribute not only to genre conventions, but also to its creator's previous work. Just like Carrie Mathison of Homeland, Odum's methods are unconventional and his sanity questionable - superior-officer-slash-object-of-sexual-tension Crystal McGuirk (Ali Larter) neatly expounds in the first 10 minutes that "three out of four shrinks found him unfit for duty". And that's before Odum is accosted by a mysterious hooded stranger intent on warning him that life as he knows it is as much of a "legend" as the stories he and his fellow agents spin as part of their undercover work. Beyond its broader conspiracy arc that has already claimed two lives by the end of its first hour, Legends is set up to tell different, barely comprehensible terrorist-by-numbers stories each week for which Bean will likely be expected to don various accents, accessories and silly hats.

Sensibly, the lead has been allowed to keep his English accent when not in character thanks to a "father stationed overseas" - this first week he appears to be playing a hillbilly Walter White, complete with terminal cancer sob story, so who knows how he would have sounded had he gone full-time American. The show is slick and preposterous, full of youthful agents with the ability to create credit ratings and health records with the click of a mouse, and – at least at this early stage – seems far too pleased with itself to allow this viewer to suspend her disbelief. Particularly since the only route of Larter's senior agent into the field is to improvise a role as a stripper.

That The Strain (****) – so clearly lighter on the production budget and all-star cast – was the one to suck me in was a surprise, but although all the pre-show publicity hinged on ancient vampires and monster curses it turned out to be a good old-fashioned horror story along similar lines as the best standalone episodes of The X-Files or Fringe. Like Odum, the leading man in The Strain, epidemiologist Ephraim "Eph" Goodweather (Corey Stoll, pictured above) is a crotchety genius; like him he's struggling to win back an ex-wife and a son and, just like in Legends, Goodweather and his shapely female co-worker smoulder away even as they try to figure out the mystery of an aeroplane which landed with 200 apparently peaceful, but very dead, souls on board and a giant, gothic-looking coffin in the cargo hold.

After Twilight, True Blood and an entire shelf-full of "paranormal romance" fiction in yer train station concourse WH Smith drained vampires of their horror and pumped them full of sex appeal, it's refreshing to see the story re-told as a modern-day epidemic, with - at least in this first episode - plenty of terrorist intrigue thrown in for good measure. It's clear too from the inclusion of David Bradley as an irascible antiques shop owner/vampire hunter type taking even fewer prisoners than he did as the first Doctor in An Adventure in Space and Time that later episodes will gleefully genre-mash Outbreak and Van Helsing: and, if a final, fabulously creepy scene involving a parasitic vampire worm and Neil Diamond's "Sweet Caroline" is anything to go by, it will scare the pants off you while doing so.