I'm an EC member, so I'm not sure if everyone will be able to read the full article at this link.

The tl;Dr is that the Garmin Varia RTL 515, the OG of radar tail lights, is the best. Wahoo's newer unit is good, but has a lousy mount. Trek's Carback works fine, but doesn't live up to the range claims. Other smaller brands (Magicshine, Bryton, etc) are also-rans.

Just thought I'd drop this here, since the topic comes up occasionally in this subforum.