Svetlana's are OK in my Marshall Super lead. Very good in My DSL40CR however.
I tried original Wing C's about 15 years ago in my Marshall Super lead & they were just OK as well; nothing spectacular like the all of the hype would suggest.
The JJ 6CA7s I replaced the Wing C's with blew them away. The JJ 6CA7s are by far the best sounding power tubes for my vintage Marshall. Next would be the Ruby EL34s.