Never heard it called sunscreen before, but both will help block the heat equally. The blackout will just also totally block light.

@ShadyLady2u Sunscreen lets a little bit of sunlight in, while blackout, doesn't allow any light to pass through. Thank you for the help!

A sunscreen blocks some heat and UV rays and allows you to see the view a blackout blind is exactly what is says it blacks out the sun. BTW if you want sunscreen to do the job go dark instead of white it is much better for keeping the view.

@Patricia I don't mind some sun rays coming through, my main purpose is to trap heat and not let it penetrate the room as much as now. Dark colors tend to absorb more heat into the room, which will make it even hotter. If both the white sunscreen and white blackout trap heat equally, but sunscreen allows some light in, then i'd definitely go with the sunscreen. Thank you for your input!

@Glo What shades do you mean please? Also, when you say a trellis, do you mean the curtains?

The dark sunscreen does not have an effect on the heat into the room but it provides a much better view of the outside keep the screen at 10% it works very well .This is what I meanI have been using solar shades for heat and UV protection for years in clients homes and they always work with dropping the inside temperature

Here's an example of what I mean by a trellis:

Citrus Ranch Property One · More Info

Pergola and Patio · More Info

La Mesa · More Info

A trellis over your deck will help block the sun's heat better than the two shades you're deciding between.

The shades I was referring to are the two shades you are asking about. The difference between their ability to block heat is nominal, so chose whichever you like best.

My own approach to this problem was to (1) replace the windows with low-e glass, (2) hang a UV-blocking screen inside, and (3) hang a second UV-blocking screen outside. I don’t know if all this terminology is right, but that’s the general idea. The new window was expensive, of course, but afterward I was much more comfortable and the summer air-conditioning bill decreased somewhat. I also had more confidence that my furnishings would be protected.