Two recent additions to the lab, after some years with a 34401A, have been both a 34465A and a DMM6500.
I have to say, of the two, I do prefer the DMM6500, predominantly because of the digitiser function... a function I never knew I needed. The touch screen UI of the digitiser on the DMM6500 lends itself far better to exploring the graphs compared to the 34465A, although overall the UI on the DMM6500 takes a bit more patience to get used to. For a start, the graphs are significantly larger on the DMM6500 display, and the screen resolution is much better (5" 800x480 vs 4.3" 480x272). I'd prefer it if the DMM6500 graph axes labelled themselves a bit better, using appropriately rounded values. I think the DMM6500 UI could still be improved upon: the UI thing does seem to be common theme on modern UIs at Tek/Keithley, they sometimes seem to have been designed and cobbled together by a committee, with little in the way of end user input (pun not intended).
In simple continuous measurement mode, I do prefer the display on the Keysight, it's a lovely clear display. The touch screen on the DMM6500 inevitably does attract finger marks of course.
The DMM6500 boots about twice as fast as the 34465A, but neither are anywhere near as fast as the 34401A, so the 34401A remains on the bench as a result!
So yes, if I were to select one of the two it'd be the DMM6500. Better still, order both.