Pico 4444 is interesting
differential scope for power stuff (12/14bit), but 20MHz is max and even that not with all probes. 3405D seems reasonable, but only 8bit. However 3000 is only Pico where can have 4ch analog + 16ch MSO. For MSO part I have come up with a way to generate up to 16 bit extra analog channel "tunneling" it thru digitals, or more lower bit ones:
https://www.eevblog.com/forum/testgear/what-you-do-with-math-channels-on-oscilloscope/msg1130997/#msg1130997Speed will limited by MSO part sampling rate and how good external hardware is (I used Arduinos).
If choose between 3405D and 3404D
MSO then latter will be cheaper but probably display -3dB at approx 100MHz if anything like other Picos. On the other hand... 3405D probably 130...140MHz.
Edit: Noticed big difference in timebase accuracy: 3*0[5|6]D have 25x better timebase accuracy +-50ppm vs +-2ppm.
As for U2701A, I looked one time at their software at it seems more geared towards using with (large) array of other instrumentation in modular system, than standalone scope application. Also it seems to lack: ETS, signal gen, protocol decoders. Also no mention of wfm/s rate. Pico is max 100kwfm/s in "persistence" mode, 1.6Mwfm/s in 10kwfms burst in segmented mode. FFT is 1.2kpts on Keysight vs n*2Mpts on Pico.
For other info heres my still uncomplete review of 2000:
https://www.eevblog.com/forum/testgear/picoscope-2000/Seems that 2000 is out of luck regarding new analytical feature called "Deep measure", described here in context of automotive scopes:
https://www.picoauto.com/support/topic17711.htmlOtherwise most should be similar.
BTW for anything high energy I also use differential probe. For low energy worked with 100x on HV but
must keep it DC coupled at all times when DUT voltage > scope tolerance (+/-20V)! AC coupling capacitors charge to full average DC value at the tip of the *x probe without attenuation.
In automotive world they use these also:
https://www.picoauto.com/products/test-leads/101-attenuatorBut "
This attenuator must not be used to measure mains voltages, secondary ignition or other hazardous voltages.". So active diff probe still seems best idea...