I have a KS34465A, DAQ6510 (same analog board as DMM6500), SDM3065X, etc. The Keithley is my favorite. I like the Keysight, but it's my least favorite 6.5 digit meter.
Of the 3 companies, Keysight support is the most lacking IME. They're not terrible, and they do seem to try, but they're slow and often tedious to even get info from them. It took them 2 months to tell me the latest firmware version for my V3500A, and they still haven't got me pricing for calibration or fw upgrade.
Keithley's support has been exception, Siglent great, and Keysight is just odd.
Thanks,
Josh