I also mix the two strategies. Usually I don't make a "build" as such, from 1-20; I build the character at whatever the starting level is (occasionally, even making deliberately suboptimal choices because I think it's what the character did at whatever level the choice was made), and then keep a few choices in mind for the next level or few ahead of where I am.
Like, as a Sorcerer, I'll be constantly thinking about what spells I'm taking next level-up, or whether I want to take Disintegrate immediately upon hitting 12th, or so forth.
My current PC is an Alchemist 10 with the Psychonaut Archetype, who was originally conceived as a poison-focused guy but certain other abilities proved attractive enough for me to take them over poison. So for example, I have Smoke Bomb because it's necessary to get Poison Bomb, but as I also took Blinding Bomb once Ultimate Magic came out, I'm now thinking of Sunlight Bomb as my top choice for Discovery at 12th. I ended up taking Bottled Ooze just because it struck me as cool (and something he'd have fun using, since his personality is basically a drugged-out hippie). Other choices, such as for feats, have been altered from original base plans as well.
IMO, this is the smartest way to play, really.
Like, as a Sorcerer, I'll be constantly thinking about what spells I'm taking next level-up, or whether I want to take Disintegrate immediately upon hitting 12th, or so forth.
My current PC is an Alchemist 10 with the Psychonaut Archetype, who was originally conceived as a poison-focused guy but certain other abilities proved attractive enough for me to take them over poison. So for example, I have Smoke Bomb because it's necessary to get Poison Bomb, but as I also took Blinding Bomb once Ultimate Magic came out, I'm now thinking of Sunlight Bomb as my top choice for Discovery at 12th. I ended up taking Bottled Ooze just because it struck me as cool (and something he'd have fun using, since his personality is basically a drugged-out hippie). Other choices, such as for feats, have been altered from original base plans as well.
IMO, this is the smartest way to play, really.