I have that 100 episode set from Treeline, too, and while I really like it, I think that you'll be impressed with the clarity of the episodes on the Critics Choice release. I'm not sure how Critics Choice ended up releasing this as most of their classic TV releases are of the standard public domain variety, i.e., usually 16 millimeter syndication prints of wildly varying visual quality (just like Alpha Video), but "Dangerous Assignment" is really a standout release for them. In fact, the clarity is so good that in the opening title sequence, you'll actually see the string that the knife rides along passing directly in front of Brian Donlevy's face!
Speaking of Alpha, they've released several shows from the Cold War/espionage era including their own volume of "Dangerous Assignment," Robert Alda in "Secret File, USA," Cesar Romero in "Passport to Danger," and Jerome Thor/Sydna Scott/James Daly in "Dateline Europe" a/k/a "Foreign Intrigue." If you like "Dangerous Assignment," chances are good that you'll like these other titles as well, though none of them look near as good as the "Dangerous Assignment" release from Critics Choice. Alpha also has a few volumes of "Racket Squad" and star Reed Hadley's other TV series "Public Defender." Here's the link to Alpha's "Classic TV Series" page:
http://oldies.com/genre/view.cfm/genre_tvser.html