In my opinion, the answer is, neither.
I have three Jadis amplifiers, all can take EL34/6CA7, KT77, 6550, KT88, and KT90. And, I have to say that I prefer EL34/6CA7 (Mullard, then JJ) best, followed by KT77 (only tried JJ). Sovtek 6550 were the worst I've tried, followed by Ei KT90, then EH 6550, then EH KT88.
Presuming you employ the right driver tubes, the bass and overall power will not be much different (I've even found JJ KT77 to have a more bass in my DA30 and DA60 than the EH and JJ 6550 and KT88s I've tried), but the midrange will be far and away better.
I have three Jadis amplifiers, all can take EL34/6CA7, KT77, 6550, KT88, and KT90. And, I have to say that I prefer EL34/6CA7 (Mullard, then JJ) best, followed by KT77 (only tried JJ). Sovtek 6550 were the worst I've tried, followed by Ei KT90, then EH 6550, then EH KT88.
Presuming you employ the right driver tubes, the bass and overall power will not be much different (I've even found JJ KT77 to have a more bass in my DA30 and DA60 than the EH and JJ 6550 and KT88s I've tried), but the midrange will be far and away better.