Most of Sony's fe zooms are around the same weight (with some small benefits at wider angles) as an equivalent canikon lens, but it's the wide angle primes that

Most of Sony's fe zooms are around the same weight (with some small benefits at wider angles) as an equivalent canikon lens, but it's the wide angle primes that you'll get a big size and weight benefit over full frame glass. The comparisons are complex, and lining up equivalent lenses only works sometimes, because many DSLR wide angle lenses are just zooms, since the primes are large anyways. Mirrorless lens designers have also doubled down on wide primes (like laowa's 15mm f2, or voigtlanders FE ultrawide primes) some of which don't exist for DSLR because they wouldn't be a good value/weight. But the mirrorbox in a DSLR means that the lens can't get super close to the sensor. So a 24mm DSLR lens will actually be a 40mm or so, with reducers put over the front. This means you get a larger lens overall, with more elements. So if you are going to go 16-35, 24-70, 70-200, then you won't see much size benefit. But if you shoot wider/standard primes, there are a lot of compact options for full frame mirrorless.