Reading up a lot about military vehicles, it's a trend that I've noticed. During WW2, while the US Navy was trying adopt a more capable naval fighter, the F4U Corsair was rejected for the slightly slower F6F Hellcat for its more forgiving controls. But during the war, the Marine Corp would make use of the F4Us with great success.
In Vietnam, while the US Army rejected the M50 Ontos, Marines used it to great effect, even when the vehicle was being phased out before the war had properly ended.
And more recently in Desert Storm, the Marines Corp was stuck with upgraded M60 Pattons, while the Army had already adopted the M1 Abrams. Since this seems to be a pattern, I'm a bit curious to know why this is the case.
I don't feel qualified to talk about the larger question being asked, but can speak on the specific topic of the Marine Corps adopting corsairs.
The main issue with the F4U corsair from the U.S. Navy's point of view was the difficulty of landing it on an aircraft carrier. The long nose and large engine cowl made it very difficult to see downwards to the front. Navy pilots found that on carrier approaches they could not clearly see the carrier flight deck and that made landings very dangerous.
The Marine Corps, however, primarily operated from land bases. There is a lot more room for error when landing on a runway rather than a carrier deck, so the visibility problem is much less of an issue. The corsair did outperform the hellcat in several ways. So in this case the marine corps was actually getting a superior aircraft for its purposes.
Eventually the British fleet air arm perfected a method for landing on their own carriers using lend-lease corsairs. They found the visibility issue could be mitigated by taking a curving approach to the flight deck that let the pilot see the deck from an angle rather than straight ahead, turning to line up with the deck only in the last few seconds of approach. The U.S. Marine Corps eventually adopted the British approach methods and occasionally operated corsairs from carriers late in the war. The Navy saw no need to adopt the corsair because by the time safe carrier landing methods for the corsair were worked out, the Japanese air forces had been decimated and the hellcat was more than good enough to take on the remnants.
Although narrowly focused, I do touch a little on the M1 development wrt Army and Marines here.