Alan,
In some ways dialing a prop with electric is easier, well certainly more accurate if not easier.
Yes to get a real feel for what its doing, you need to maintain as much constant as possible, so adjusting lap times would be a good approach IMHO. However, that being said, If the lap times are close, it might be interesting as well, to explore how they manuever at the same setting.
with a glow engine, the needle setting is somewhat less predictable because the engine responds rpm wise to the load. In some of my experiences with glow, I have swapped two props that are just minutely different and left the needle the same.
Bottom line,, it does take time, and attention to detail to get any valid information comparatively with props.
Is it worth it,, I would say most definitely. I have had props that fly the plane at exactly the same lap times, and perform VASTLY different in maneuvering. I have had a setup that felt really good, and then experimenting found out that it wasn't as good as I thought it was when I bolted THE prop on there and flew it. BIG noticeable difference at the handle.
Is it worth YOUR time ? only you can decide, you may find that what you have is in fact the optimum,, however in my humble opinion, the act of experiementing, and trying different props is worth it if for no other reason than to increase your awareness of how the different parts of the system interact.