Seek-Locate-Destroy is the one which introduces Blake's foes Travis and Servalan, in a scene of crackling testosterone. We also get the unexpected bonus of Peter Miles (Nyder in Genesis of the Daleks) as Secretary Rontane, demanding Blake's head, and some lovely lines from Vila: "Tell him I've just worked out a completely new strategy. It's called running away." "There isn't a lock I can't open - if I'm scared enough." Nice character bits as they attack the complex in the first half of the episode.
Unfortunately after that first scene with Servalan, Stephen Greif seems to rather lose interest in playing Travis and Terry Nation rather loses interest in giving him anything interesting to do. The core of the plot is promising - Blake risking all to rescue captured Cally - but in the end it is rather disappointing that he simply teleports through the defences that Travis has laboriously set up precisely to prevent him from doing so, and the dramatic punch evaporates.
Mission to Destiny is an interesting example of B7 veering into a completely different genre, as essentially a locked-room murder mystery on board a spaceship, with a subplot of Perilous Journey for Blake and the others. Avon solves the mystery and gets one of the best quotes ever. (Cally: "My people have a saying, 'A man who trusts can never be betrayed, only mistaken.'" Avon: "Life expectancy must be fairly short among your people.") John Leeson, the Voice of K9, plays one of the spaceship crew whose mutual antagonisms support the plot. We also get a glimpse of life on human planets outside the Federation.
It all works except for the Liberator sub-plot, where the timings (desperate run to the planet Destiny, through the meteor storm, yet somehow back again in time to catch the Destiny crew before the bad guys arrive) just don't work out. Also it might not have been a bad idea to check that there was something in the box before risking life and limb for it.
As for Duel, it is essentially an interesting variation on the equivalent Star Trek, Frederic Brown and Longyear - most notably, that Blake and Travis get their companions as well to help them. Again, Avon gets the best line ("Blake is sitting up in a tree; Travis is sitting up in another tree. Unless they're planning to throw nuts at one another, I don't see much of a fight developing before it gets light.") Some good special effects especially as Liberator rams Travis's ship.
As always with this type of story, I am bothered by the fact that we don't get a good handle on the means and motivation of the god-like aliens. Poor Isla Blair, playing Sinofar, was obviously rather cold. The concept of the Mutoids is good and well explored though.
Project Avalon works perhaps the best of these four episodes. It is strangely reminiscent of a couple of Terry Nation's Doctor Who stories - the whole underground lab reached through a cave complex thing from Genesis of the Daleks (and indeed The Daleks), the androad doubles from The Android Invasion (and less seriously The Chase) and the super-vicious virus from Death to the Daleks! (and references also in Genesis). Here he has boiled some of his own favourite themes together to make a decent drama.
I still don't like Stephen Greif as Travis, but I did like the changed relationship with Servalan, she now is putting him under pressure to deliver (and I'm not really sure that his assertion that he could have eliminated Blake but for the Federation's insistence on capturing the Liberator is supported by that we have seen on screen). A lot of fans don't like Julia Vidler as Avalon but I think she's OK, both as Avalon herself and the android double. Some decent special effects as well. Vila and his heat suit is hilarious. Even Blake gets a good line ("They probably tried to surrender...). The best of these four. Apart from the stupid robot.