I have owned and/or heard a number of EL34 and Kt88 amps. I generally agree with the comments that the KT88 is more balanced and extended and the EL34 is "fuller" in the mids. However, as they say, execution is everything. The Vac Avatar that I recently sold used EL34s. In UL, it was close to the sound of the VAC KT88 amps. In triode, with the right speakers (moderate impedence & eff. of 88-92 db.) the midrange could be sublime; not overly rich or warm, simply right, exceeded only by a few of the very best tube amps. Still good extension on both ends, maybe very slight roll-off on treble with deep bass but of course not as much slam as SS. A couple months ago I had the opp. to hear VAC's new top of the line $19,000 integrated, which I believe uses KT88s instead of the 300Bs that most of VAC's more expensive amps have used in the past. Its sound was similar in character to the Avatar in triode, except better in every regard. Perhaps the best amp I have heard. Intimate yet dynamic and detailed.
TLH
TLH