When you consider there's slightly more than 453 grams in a pound, probably not much, but I might guess the flex and kick point position would mean more to your swing dynamics than the simple weight of the shaft.

A little bit heaver of a shaft will not let the club torque as much.  I use a 76 g shaft x-flex and I love it.

If you use a 65 g shaft, it does feel a little lighter and it will allow you to swing a little faster and get better club head speed.

Also, with the heaver shaft, you get a little more control in my opinion.

this is just my opinion though.

I agree with a little of both. I think though with your swing speed tat the x shaft is not a good fit. you might notice you pull or duck hook your shots since the head will remain closed or get closed a little quick for your hands