^^^The mains are the primary influence on the stringbed, so whatever you put on them will provide the overriding influence in terms of characteristics like feel and power.
I did try a hybrid the non-traditional way round (i.e. multi mains, poly cross) by accident when I wasn't concentrating on what I was doing. There definitely was more power and a softer feel. I will be trying it again at some point and comparing it to the same strings the other way round, but I prefer poly mains in my hybrids as I prefer the feel of poly.
ERSA MRT & Pro Tour Stringer
Head i.prestige. Unstrung specs: 340g, 320kg/cm2, 30.5cm