Two totally different movies... apples and oranges.
Newsweek
As brutally unsparing as “Platoon” was, it was ultimately warm and embracing. Kubrick’s film is about as embracing as a full-metal-jacketed bullet in the gut. [29 June 1987]
TV Guide Magazine
A perversely fascinating movie—one that answers no questions, offers no hope and has little meaning. In a way this is perfect for what the film has to say about war, but you find yourself numbed and apathetic as the film progresses.
Wall Street Journal Julie Salamon
By most standards of conventional film narrative, this movie is a mess. [25 June, 1987, p.22(E)]
San Francisco Chronicle
The concluding image of men silhouetted against the dying flares of explosives, as they march to the raucous refrain of the Mickey Mouse Club theme, is masterly, but leaves a viewer curiously discomfited. Whereas “Platoon” shattered civilian complacency about that war, Full Metal Jacket is merely numbing. [26 June 1987]
The New Yorker
Pauline Kael
What happened to the Kubrick who used to slip in sly, subtle jokes and little editing tricks? This may be his worst movie. He probably believes he’s numbing us by the power of his vision, but he’s actually numbing us by its emptiness. [13 July 1987, p.75]
They were both crap! Platoon was an atrocity - full of BS tropes about our war in Vietnam and cheesy special effects.
Full Metal Jacket had an OK boot camp start but with an unrealistic finish - and then went into its caricature-filled stupidity with its "Hue City" part that had no resemblance at all to the real Hue City or real Marines or anything else combat-related.
All of the big-budget movies about the Vietnam War were unrealistic and insulting to the good guys who fought that war.