Chungjh, I owned both CAT JL1’s and then JL3’s. I had them for approx. 20 yrs., and had only 3-power tubes with issues during that time. So, they weren’t hard on tubes at all.
As I believe I previously mentioned, when a tube blows it takes a resistor with it. The resistor is soldered to each power tube socket. The resistor acts as a fuse. That was the case with all 3-power tube issues I experienced over the years.
As my hair grayed, arthritis progressed, leaving me with the use of walking aids. Because of this, owning a pair of ~190lb./ea. monoblock amplifiers became less and less prudent. Unfortunately, this was compounded by the resistor issue. I can still remove a fuse; but I can’t move, let alone flip-over a 190lb amplifier; remove the approx. dozen screws from its bottom plate and then de-solder a resistor and solder another in its place. If I weren’t disabled, I would not have dispensed with the CAT’s.
There obviously is no best of anything in our wacky hobby. However, among high power push/pull amps., the triode CAT’s must be placed in the very small mix of the best. They will drive virtually anything and will do so with prodigious bass, coupled with SET-like purity in the mid’s and highs.