The Ka service is ~70Mbps per plane due to the ability to do spot beams with Ka, which are LEO (low earth orbit).
Neither of these statements is true. The total capacity to each aircraft is lower than that (though potentially can be that high, it is not provisioned that way today) and it is geostationary satellites, not LEOs, in use for Ka coverage. And Ku coverage.
It's unfortunate that they had to use two different vendors for the systems, but that's the reality of satellite technology nowadays - the manufactures insist on an end-to-end ecosystem to keep tight control over the system.
It has absolutely nothing to do with "control" issues and everything to do with getting the correct mix of coverage and performance and price for the different subfleets.
Side note: ViaSat, the company behind the Ka system, is in the process of launching additional satellites that will make trans-Atlantic and trans-Pacific crossings possible with the Ka equipped birds with only a small antenna change.
The only pending launch from ViaSat is ViaSat-2 which adds LatAm and TATL to Ireland. There is nothing public from the company re Pacific coverage.