Best method to determine current in ESR meter
Sorry for the delay.

After testing both methods using various shunts(.01, .05(1%, .5%, no idea)  and CT's(4 hand wound and 2 commercial (small value burden and tried with both with no gain and gain))), I'm going to go with a shunt.  The CT's ended up having various phase errors that were in 1 case very non-linear(but that could have been my error, it was one of the home made ones).

The way I tested the them was:


Using a Function Generator set to 100Khz and then setting up a sweep from 1Khz to 100Khz with slow steps and .25 to 3vpp. 
For a reference resistor I used a couple of old 1 and 220 ohm .5% mil-spec resistors (still on the reel) I picked up at a ham-fest years ago. Through hole, blue and lots of bands..:)
The best I could do for the DUT were a some 5% film caps 104J and 163J.  I was too lazy to make any inductors(The only ones I have are either low-Q crud or much better rf air core(I guess I could have taken one of the tank coils out of an amp, but that would have been overkill plus work), neither of which I thought would be helpful here)


Then I would observe the wave forms using my VDS1022(25Mhz) (I used a Kikusui 5060(60Mhz) to confirm that the DSO traces at least resembled reality) Then a screen cap was made.

After comparing them the shunts were all in line, meaning no surprises.  The CT's were not bad, meaning they were fairly consistent within a device, but when compared to each other or the shunts, there was differences(Would the term jitter also apply here??).

Since I'm easily able to control by excitation and gain, the shunts just make it much easier without having to play follow the leader trying to tune a CT circuit or apply corrections in software.

Please note, the final application will end up being a LCR/ESR meter.  I doubt I'll ever go over 50V or 1A.  On the other hand I think if your dealing with trying to measure mains the inaccuracies of a CT really do not matter.  The simple fact is that the chance of your voltage/current wave form being nicely symmetrical, of whatever shape, is so close to 0 as not to matter, meaning a little bouncing around really will not affect the measurements.  And using a CT or Rogowski coil makes it much easier to measure your 120V+ at whatever current.