All three types never advanced beyond prototypes. Moreover, of the three, only the XP-72 could be considered a viable fighter. According to Republic (who designed and built the XP-72s), 37 mm cannons were never considered. The original Army specification called for the cannons, but was revised when faced with the fact that it was a pipedream.
During test flights, one of the XP-72s attained 490 mph on 3,000 hp. Pratt & Whitney promised 3,450 hp for the production engine, which would have allowed the XP-72 to attain speeds well above 500 mph. Had the Army wanted them, P-72s could have been rolling off the line by the spring of 1945. However, the need for these aircraft was virtually eliminated by the P-80 and the Army cancelled the program, giving Republic a contract to design and build their own jet fighter, the XP-84 Thunderjet.
Lockheed's XP-58 was a massive fighter, obsolete in concept before it ever flew. Convair's XP-81 was a mixed power fighter, using both turbojet and turboprop power. Even if a sufficiently powerful turboprop engine were available, it still would have been a great deal less capable than the P-80. It was a huge fighter, and range would have been no better than a pure jet. Inasmuch as it was still more than a year from being sorted out, the Army cancelled the project.
My regards,
Widewing
