12ax7 vs 5751


hi all,
i need some advice. i`m very new to tube amplifiers and i`ve been doing some tube rolling.

i currently have a pair of grant fidelity matched psvane 12ax7t`s in my amp which sound fantastic.

what i`d like to know is which are the better tubes, 12ax7`s or 5751 tubes. i`ve been looking at forums and there are folk out there that say 5751 tubes are better than 12ax7 tubes.

can i have your thoughts on this please and also which are the good 5751`s to go for.

i really like the psvanes but if they can be bettered i`d go for it as my next line up of replacement tubes.

my amp is a yaqin mc100b. the tubes i have installed at the moment are.....
2 x psvane 12ax7t`s
2 x brimar 6sn7gty/cv1988`s
2 x sylvania 6sn7gtb`s
4 x electro harmonix kt88eh`s

many thanks in advance guys.
grayf
I guess it is no big deal...but the posting I responded to had the 12at7's listed as made in France. Then they are labeled GR BRITAIN. I really dont know enough about tubes to know the tricks of the trade...Are all bugle boys labeled GB?
I started listening to the Bugle Boys today. Right out of the box the overall presentation is smooth compared to the Golden Dragon. Any ideas on a decent break in period?
Im gonna wait a bit and do A/B comparison.
From what I know, different models are best from different sources. For instance the best "Amperex" 5AR4's were from GB (they're actually rebadged Mullards). Their best 6DJ8 was from Holland. Also keep in mind that Amperex never actually made a tube called "Bugle Boy". If those words actually appear anywhere on the box or the tube itself, it's probably an eastern knock-off. Those might be fine tubes, but they're not genuine. Anyway, I don't know what source is the best for 12AU7's or 12AT7's. I can say that I've never heard anything bad about an Amperex from Britain, France, or Holland.
There is an acid etched code on the tube that will tell you where the tubes were really made. Phillips owned both Amperex and Mullard brands and cross labled many of their tubes. If they were made by Phillips they will flash upon start up and have typical cross molding marks in the glass on top of the tube. In any event if made in Great Britain it should sound rich and mellow like the Mullard tubes do. The Amperex Holland tubes have a cleaner and 3d imaging with better detail in the top end. All the comments on sonics are IMHO of course.
Mechans
Rich and mellow compared to the Golden Dragons is a good description. For my set up rich and mellow is a good thing. Once I compare side by side, I will share my thoughts.
Thanks