What Full-Frame means in practice
A full-frame sensor at 24.2MP gives the shallowest depth of field of the three formats at any given framing and aperture, and the most sensor area to gather light with. That is the physical reason full-frame bodies tend to be the larger and heavier option: the lenses that cover the format have to be bigger too.
Video, stabilisation and weather sealing
4K tops out at 30p, which covers standard delivery but leaves no room for slowing footage down. 10-bit recording internally means colour survives grading rather than banding when pushed. A log profile is available, which trades a flat-looking file for latitude in post.
In-body stabilisation steadies any lens mounted on it, including primes with no stabilisation of their own. The body is weather-sealed.
