That's always a hard decision. It depends on the genre though. If it's an anime with Ecchi or violent scenes then I'd definitely wait for a BD release to get the full experience.
But with slice of life shows that are set it school or university it doesn't really matter that much whether you watch the BD or TV version
Once I make space for it I plan to get the Prison School BR since the tv release was censored. Was gonna rewatch OP Man in BR but apparently there are quality issues with it.
depends on the series. i think im gonna buy the full collection of steins;gate because it was so damn good, and of course ill rewatch it then.
edit: wording.
depends on the genre. if it´s an anime with very violent/ecchi content, i´d just wait for the blueray release before watching it in the first place.
if it doesn´t have any of that, i´m perfectly fine with watching the TV version and leaving it at that.
That's one of the reasons I don't buy them even when I do have money. It's hard for me to buy something I've seen free repeatedly and even when I do buy them I realize I don't really want to sit and watch it. I've got 2 seasons of Yu Yu Hakusho just collecting dust.