I use a Redhawk with the factory mount system and a 2x Burris for hunting under similar curcumstances........and I favor the the heavy 270 or 300 gr slugs (plain jane .44 magnum) for the longer shots because they seem to pack more energy past 100 yards . Sight in dead on @100 and you only have about 6 inches of drop to deal with at 150 yards. Very accurate range estimation is crucial though as past 150 the .44 loads will drop like a rock . The Redhawk is very accurate with 3 shots touching at 50 yards (scoped) and with a solid shooting posistion , 150 yards is duck soup. Killing power is really not a problem , 300 gr XTP s will drill thru a whitetail like swiss cheese .

I wouldn't mind trying out a .357 max revolver some day , as I think you might gain around 50 yards trajectory advantage .........

The 454 is a great handgun to shoot out to the 150yd mark as a 300 grain bullet traveling 1700 fps if sighted in for 100yds is only 1.1" high at 50yds and only 5.8" low at 150yrds keeping the rise and fall within 7". It still has 1017 foot pounds of energy (about the same as a 240gr 44mag bullet at 50yrds) as it is still traveling 1235 fps which is more than enough to knock down any Whitetail deer.
As long as you can group within an 8" circle at 150yrds don't worry about taking the shot, just make sure you can hit within this target from all the positions you might shoot from. For me i will not take a shot at a deer at that distance unless i can use something for a rest to steady the shot.
I use a scope on my Ruger SRH 454 9.5" and with the cast bullets i use i was breaking clay pidgeons at 200 meters from a rested position,so don't let anyone tell you it won't work at 150yrds.