Curtains vs blinds for the best blackout for your bedroom windows.
This might be your first decision and will rest on aesthetics and room and window design.
In most cases, full-length blackout-lined curtains will provide the best blackout, especially when combined with a corded track and either a covered lath and fascia or a pelmet.
A top-fixed corded track will afford a good level of blackout, but combining it with a covered lath and fascia or pelmet will further enhance the blackout. Corded curtain tracks benefit from an overlap arm, and the tension prevents springback.
Covered lath, fascias, and pelmets are also great if you want a second lighter curtain for privacy, as both tracks can be neatly hidden. And if you have privacy roller blinds in addition to blackout-lined curtains, a pelmet will hide the tops of the blinds, which can be a nice style benefit.
However, choosing between a track, covered lath and fascia, or pelmet will depend on which is most suitable for your window.
If you are renovating your home and are installing a new cornice, consider creating pelmets with the cornice to hide curtain tracks.
Curtain poles will always allow more light to enter.
If you prefer the look of a curtain pole, be prepared for more light creep, but you can take measures to minimise this—for example, position the pole as high as possible above the window or go for a glider pole (a pole with a track inside, rather than rings) so that the curtains sit tightly under the pole, again positioning it as high as possible above the window.
Radiators provide another challenge to blackout.
If you have a deep radiator under the window, you will need deep brackets for the pole to allow the curtains to reach the floor in front of the radiator. To get a great blackout, the curtains must touch the floor, but of course, your curtains are now some distance from the window, and light will come in at the top. Everything is a compromise!
In this instance, a better option might be to have a top fixed track or pole that attaches to the ceiling.