P94 and P944 are catalog differentiations for the same gun in different caliber chamberings-the P94 for the 9mm varients, P944 is the designation for .40 varients. All are rollmarked "P94" on the slide.
While the .40 varients of the P94 were first produced with a swinging link, and subsequently with the camblock system, both are catalogued as "944s" with no cataloging designation differentiations that I'm aware of; Ruger simply made the shift at some point in the late 1990s as I recall with little fanfair, probably for reasons of manufacturing standardization/efficiencies more than anything else-I'm unaware of any inherent weakness attributed to the swinging link system in the P94 series (which Ruger continued to use in the concurrently produced P89 and P90 series).
Similarly, in Ruger's catalog system, the letter "K" preceeds a stainless steel varient; i.e., KP944 would be a stainless steel .40 P94-but you'll never see a slide rollmarked "KP94" or "KP944"-all are just rollmarked "P94".
Unfortunately, author Patrick Sweeney has unknowledgeably (and inaccurately) perpetuated the confusion on this issue in his otherwise quite good recent book, "The Gun Digest Book of Ruger Pistols."