I have both blinds and curtains and since getting the blinds we don't close the curtains, except in the kitchen where we tend to close the curtains as it is easier than reaching over to drop the blind. We find the blinds very useful though for cutting the glare of the sun (we are south facing) In the kitchen we have venetian blinds and when the sun is causing glare we turn the slats upwards slightly so that it blocks the downward projection of the rays but still allows some light in - you know what it is like if sunlight is shining into the kitchen - it will find something reflective to shine on and blind you every time you walk into the kitchen.
Dawn