More helicopters in WWII

Another WWII scenario- WI there'd been more extensive development of helicopters and vertical-lift technology by both the Nazis and the Allies ? Would there have been more advanced choppers than the German Flettner KOLIBRI (Hummingbird) and US Sikorski designs, and would there have been a greater employment of choppers for purposes other than SAR ? Could there have been tank-killer German choppers being the equivalent of 1940s-era Apaches over the Eastern Front, or as in LAST TALONS OF THE EAGLE the massive German chopper (whose designation and name escape me) flying the huge tons of supplies to von Paulus' 6th Army Group at Stalingrad ?
 
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