A good wide angle lens can be tremendously useful for a range of photography genres, and Canon shooters have a few options from which to choose, with varying image quality, specs, and, of course, price. The excellent video comparison takes a look at three such lenses, the RF 14-35mm f/4 L IS USM, RF 15-35mm f/2.8 L IS USM, and RF 16mm f/2.8 STM.
Coming to you from Gordon Laing, this great video review compares the Canon RF 14-35mm f/4 L IS USM to the RF 15-35mm f/2.8 L IS USM and RF 16mm f/2.8 STM. With prices ranging from just $300 to $2,400, these three lenses cover a wide variety of needs and uses. Personally, if you are stuck between the two zooms, I would recommend going with the 14-35mm f/4, unless you absolutely need that extra stop of aperture for something like astrophotography. Not only is it much smaller and far more affordable, the difference between 14mm and 15mm is not insignificant, and if you are a landscape or architectural photographer, you are likely to appreciate that extra stretch on the wide end. Check out the video above for Laing's full thoughts on all three lenses.
Didn't watch the video, but there's an important disclaimer: You need a lens profile for your RAW converter for either RF 16/2.8 as well as RF 14-35/4, as they are not calculated for uncorrected viewfinders (you can't turn of lens correction in cam). That means that you might be pretty lost if there's no lens profile, as both lenses deliver nice Jpegs and pretty awful uncorrected RAW files you probably can't correct perfectly with applying simple and straightforward distortion correction. That happened to me with Capture One with the RF 16/2.8, and the 14-35/4 suffers from the same problem at 14mm. Why? Both have shorter focal length with a lot of distortion, quite fisheye-like, and a bit of real physical vignetting (really dark corners) and a bit of moustache distortion. Both are calculated for in cam distortion correction, so there's space enough for cropping as they are significantly wider than 16mm (or 14mm).
If you are Jpeg-only shooter, go for them. Both are nice lenses. I sold the RF 16/2.8 and bought a decent second hand EF 16-35/4 IS, which also needs to be corrected, but there are lens profiles available. If you have the money, go for the RF 15-35/2.8. There are lens profiles, and you get what you pay for.
Canon did a pretty bad job with those cheaper lenses, and processing them with their own RAW converter DPP is no fun, that crap program lacks compatibility.
(sorry about double post)
Upon leaving behind my RF - EF adapter, my UWA choice was the last lens for me to make a decision upon. I did the 16, the 14-35 and various MF UW primes. I settled on the Samyang AF RF 14 2.8 so I could get my astro and wide landscape in one with AF to boot. The 14-35 f/4L just has too many compromises for the cost. The 16 is a great deal for the money but if you're printing, any size at all, those stretchy corners are a deal breaker. I'm happy now but I went through a half dozen lenses buy and sells before figuring what worked for me. The rest of the RF lineup is great for it's infancy, I'm not expecting it to grow into the EF catalog this early and the filled gaps will come, 1.8 & 1.4 primes I'm looking at you.