Every single shotgun I've ever shouldered feels different. So, depending on LOP, drops, and other more subtle measurements, any gun, PG or straight, might feel comfortable, usable, terrible, wonderful, etc. So, it's got to feel right, and it's got to go to a cheek weld in the right spot, quickly and comfortably, either way.
So what's the straight grip really for?
If upland hunting, to you, means driving around in a 4x4, finding a field that's full of quail, doves, or whatever, hopping out of the car, and marching into that field, the straight grip offers little inherent advantage. It might look cool, it might feel better, but it's all subjective and totally up to you.
If, however, you often find yourself tromping a few miles over hills and bushwhacking through chapparal, you'll love the straight grip. You can hold the shotgun low and across, in front of your stomach, safe but ready to shoulder quickly, for a long time. With a PG, you end up contorting your wrist, which gets really uncomfortable within the first mile.
That's my $.02