Cygolite Hotshot and Hotrod are still the best values in taillights. I use both. Hotshot is clipped to the supplied mount on the seat post. Hotrod goes on the seat stay tube, lower near the hub. I find a little separation between lights helps with quick visual orientation when I see other cyclists and motorcyclists.
I've used the Hotshot 50 and 150. Both are bright enough even in daylight. When I use the Hotshot 150 at night I set it to "zoom" mode, with a slow pulsing light, or steady if I'm in a group ride to avoid blinding riders behind me. In daylight I use the more rapid strobing modes.
The Hotrod, I usually set to steady. Some observers find it easier to visually orient on lights when at least one is either steady or slow pulsing, rather than strobing. That's important at night. Less important in daylight.