In any case, it would have been better if I had a looper so that you could discount the differences in attack and volume and stuff, but yeah. The biggest difference between the two buffers is that the JFET has slightly less than unity gain, which is kinda nice as my pickup is stupid hot. But beyond that I can't hear the difference between a fet or an opamp buffer, even though they should theoretically have different impedance, which should load the pickups slightly differently, but I don't hear it. But the difference between buffered and unbuffered is massive.
For the record I'm using a JFET input buffer and an opamp output buffer running at 15v. Did it that way because I wanted to build two different buffers, and I got the impression that JFET buffers were good input buffers.
But in hindsight I'd probably just use op-amp buffers as they are easier to build (we're comparing easy with easy here). The input buffer is nice to have to make sure that the loading on my pickups isn't affected by different pedals, but it'd be easy enough to do away with. Output buffer is crucial though.