For BA its: 10in x 18 x 22 plus laptop or handbag.
For VS its: 9in x 14 x 22 (6kg in Econ and PE, 12kg UC)
The VS limit has always kept them off limits for our trips, as I am unwilling to check-in camera equipment if another carrier allows us to keep my eye on it.
Didn't BA revert back recently to higher limits? If so are all the guages up-to-date?
As a pertinent exampleon BA. Does the guage work to centimetre limits or the inches or the larger of the two? 10in is bigger than 25cm for example.
To be honest I am happy enough with gate check-in and return, for my gear ... but not it out of sight through two airports.