Controlling the valve, with regards to acceleration on and off the seat, as well as slowing it down through peak lift is why there’s power in correct geometry. The narrow sweep, and where it’s located on the stem become secondary factors, and are results of getting the shaft location (more) correct. I’d rather see good control of the valve and a little wider sweep, a little off center, then give up the benefits of valve control to narrow the pattern or center it.