Yup, they will make more power up top for sure. With a super inefficient roots blower at only 8 psi, my peak horsepower is at about 6200 rwhp with a set of mild blower cams on PI heads. That compares to around 55-5600 for a stock cam PI head car. At 6k rpm, I bet I've picked up 40+ rwhp, with no loss in low end torque.
A bigger cam does not necessarily open the valve any more. My blower cams have roughly the same intake lift as the stock PI cams, and over .025 less exhaust lift. The big difference in aftermarket cams is the duration and lobe centerlines/LSA.
These are the cams from my car. Blower cam on left and stock PI cam on right.
Notice how the lobe height is very similar (which is because they're practically identical as per the specs), but see how much fatter the blower cam is? THAT is where the power comes from.
For reference, a stock PI cam has .507 intake lift and .534 exhaust lift. A Hitech Stage I cam and an MHS Stage I cam has .550/.500 while a Comp Stage I has .550/.550. So without knowing what cam you have, it's not possible for us to tell you if that sounds right or not. As shown by the Hitech and MHS specs, it's possible the valve lift IS actually less than stock.
Actually, it's .0625", but we'll let it slide.
Also, because of the rocker arm ratio, you won't see .500 or .550 or whatever on the cam lobe. It'll only be around half that (~.6 IIRC).
Yes, there is debate on whether long tubes are worth it or not. But there is absolutely NO debate on shorties. They are 100% a waste of money.