Z - I really enjoy them both - but I've not put them up side by side, I don't think I have ever had them in the same room. The 708s and 420's have the characteristics that I enjoy in a speaker - low compression, super revealing and pretty transparent.
I originally got the 708's for my office / studio when we were in the NY area. I had sold my B&W 802's to finance the purchase of the (then new) JBL 4367. For me - the 708 was a smaller version of the 4367 that I could have at work and they had the same characteristics that I love in the 4367; revealing with tons of dynamics, virtually no compression and no fatigue.
PS - I LOVE the 4367 and those I have had in the same room as the 420's. They're my 2 favorite speakers.. I put the JBLs in storage for now because of the addition of the 870 subs paired with the 420's - but honestly, I love the sound of both pretty equally.
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