Well basically Bugera are doing what many others do (e.g. Boogie, GT, Ruby etc), they are picking the best from various suppliers, obviously they all go for low noise/microphonics, gain etc. But if you put a Boogie SPAX7 (their premium offering and usually a JJ ? from what I've read) up against a New Sensor Mullard reissue, they sound "quite" different. Both though are low noise/microphinics high gain. So from the many well tested options we talk about here, they are all low noise/microphonics, high gain etc. So it comes down to how they sound in "your" preamp with how "you" play. My 2nd MP2 came with EV 12AX7s, I wasn't impressed (but they were low noise etc etc). And blanket comes to mind as I recall them.
How/what you play makes a big difference to what will work best for you. The first tube change I did with my MP1 way back was to Boogie 12AX7s (coz I could buy them locally and hadn't thought about it much). They were fine and suited what I was playing at the time (much more higher gain than I do now). They are a very tight tube and IMO suit very high gain situations (as MJMP likes them (well he uses Ruby JJs, much the same short plate tube) in his 3TM). They also have the nicest feedback I've heard so far (important at those gains). I tried some in my MP2, as posted elsewhere here, they were ok.. The Mullard long plates introduced a new dimension I'd not experienced before, they are so articulate and "3D" which really suited my current playing style, so right now they are my preference. Many here are finding a combination of different brands (in V1,2,3) works for them, you just have to try a few options/combinations to work out what you like. But at this end of town (i.e. they are all low noise etc etc) we are commenting on/ comparing the sonic differences. But based on my experience and other comments here for those that have tried them, the Mullard Long plates are definitely worth a try, even just one in V1.