Looking back critically at my own experience, i spent too much time at making the art during the development of a game. That means i wasted so much time by refining the art... starting the game over and over...

Including the art only in the game design document would be a much better way in my mind. That means describe the style, look&feel very roughly with some sample screenshots from other games and even sketches. (In addition the whole gameplay/levels/story should be layed out there - so you can "play" the game in your mind by just reading that document.)

Then during development time i would make a prototype with just gfx placeholders, that already have the right size. Once the gameplay system is finished, so that one can play the game, i would start on working on the art part. This way you can see if the game is fun and refine it with the art and push the feeling of the game you got by playing it even further in a specific direction. This procedure also guarantees the coherence of style throughout the game.
If you decide for an art style you cant create yourself, its a good way of working together with some artist from this point on. So she/he has the freedom of creating all the assets from scratch.

The reason why so many indie games do the "art" style over the "tech" style is simply the cost in time/money for the tech style. An art game is also more congruent for an "indie" game. If an indie game has too good techie gfx, people will wonder if it really is "indie"...and worth the money.

Just my 3 cents