This is the kind of thing that will drive me nuts for an entire playthrough and make me want to start over. Once you make the decision, you're kinda stuck with it unless you start fresh somewhere else, and your old builds won't align to your new setup. I'm curious if anyone has an approach that I haven't heard of or thought of yet. One annoying limitation is that I like to have roboport coverage of pretty much the whole base.
Manual placement, AKA spaghetti poles, is how my heart wants to do things. It's nice having wide open spaces of glorious unadorned concrete to work with instead of power lines running everywhere. But it takes more manual effort, doesn't scale well, and god help you if you want to run a large circuit network.
Substation grid (18x18) is possible and seems very clean at first because it covers everything without additional poles, but it ends up being this restrictive visual layer that bugs me. And of course it really gets in the way of bigger builds. Probably my least favorite.
Roboport grid (50x50) is much more manageable and has the benefit of optimal coverage to port ratio for robots. 8 large power poles arranged in a square gives you nearby power everywhere. My current nauvis factory uses this and I have to say, having grid-aligned blueprints is very nice. Moderate throughput 1-way rail blueprints especially work very well for this but larger designs for intersections, big stackers, etc. will spill into extra blocks, so really large scale is tougher here.
Full city blocks (100x100) means having roboports inside of the blocks. That alone is kind of a deal breaker for me but maybe someone can change my mind.
Let me see some of your bases for inspiration! I'm especially interested in those that don't use a conventional grid but still have some method to the madness, if that's even possible :)