I have a Proviz Reflect360 CRS in green – they do a few other colours including yellow and orange in the CRS models.
They are incredibly reflective in car headlights at night, and with the right colour in the CRS models (CRS = Colour Reflective System) can be decently HiVis during the day. The standard Proviz Reflect360 (without CRS) only comes in a dull grey as do competitors such as the ones from Evans, and while they have the super bright reflective qualities at night they really don’t stand out during daylight. The dull grey seems to merge into the background imo.
Agree with what others have said in that the material feels quite heavy and they can get sweaty. While they have pit zips and a vent across the back they don’t match the breathable qualities of Gore Tex or similar technical fabrics so things can get a bit uncomfortable when you sweat.
It’s a compromise product and it depends on your priorities (and how much you tend to sweat). I use mine when it’s quite cold, even though I could do with the night time reflective properties all year round. I rely on plenty of lights and other reflectives when I’m wearing less eye catching but more comfortable outer layers in other times of the year.
Proviz do a couple of cuts, the standard one which is a loose ‘commuter’ style and a more fitted ‘Plus’ cut. I’ve read a few reviews that are critical of both cuts. I would definitely advise trying for fit before buying.