What affects power more in a camshaft....high lift or longer duration?

duration will impact where the peak power/torque is. the more duration the higher the torque peak RPM. the higher the torque peak (since HP is a function of torque@ RPM), the more horsepower you can make.

Lift will impact overall power potential. the more lift, the more area under the curve at higher flow levels, so the more air and fuel can be crammed in for a given duration....to a point, at least. no reason to use a .6" lift cam when your head's peak flow is at .450"

I like to evaluate 3 data points when looking at a cam lobe. advertised, .050, and .2" lobe lift durations. you need those 3 points to understand the whole story on how aggressive a cam really is. you want to maximize the .2" duration, since you get more flow at higher lifts...advertised will give you an indication of overlap (when no pressure can build in the cylinder), .050 will give you an indication of duration when any actual flow happens, and .2" give you an indication of duration when real meaningful flow for power production happens. comparing the rate of lift between .050 and .2 will also give you an indication of the aggressiveness of the cam.

for example, in my old 5th ave, I had a 360 similar to your first one....it was a stock long block '78, but with an edelbrock air gap, 600 eddy carb, hedman headers, and a comp XE262 (262 adv, 218@.050, . ran pretty damn good, I'd estimate it was an honest 330 HP. allowed my 5th avenue with a 42RH and 3.55's to keep pace with a 2005ish Chrysler 300C with a 5.7. if you look here, https://images.carid.com/comp-cams/items/pdf/comp-cams-product-catalog.pdf on page 14, you can see that the lobe has 128 degrees duration at .2" lift.

I replaced that engine with the stock '85 roller cam 318 shortblock, Magnum heads, and the same induction and exhaust. I had the cam reground by Bullet Cams, and used their HR259/316 lobe in the intake 259(adv) 208(.050) 127(.200) 0.3160 lobe lift, (.506 valve lift with magnum rockers). that engine actually pulled as hard or harder than the old 360, even though it was 42 CID smaller. also got 5mpg better on highway cruise.

That engine had a bit more compression (measured around 9:1 as I used the thin mopar gaskets available at the time), but the heads flowed about 10% better, and the camshaft, even with the 10 degrees shorter .050 duration had as much or more area under the lift curve, due to the same .200" (which if you compare the ramp if you use .050 and .2 as data points, the "smaller" reground roller actually had MORE duration at .21, .22, .23, .24, .25 etc lift than the "bigger" flat tappet).