Cool topic. I think I can be of help since I have owned all the cabs you mentioned. I also did not like the Friedman cab I had, It sounded a bit small to me... I had three other 4x12s to compare and liked all three more. Two of those cabs that I still have are the Mesa Traditional and the Splawn. The Mesa has V30s and Ive actually had more than one Splawn cab over the years as I like them a lot , I have tried a lot of different speakers in them including v30s and greenbacks.
I like both cabs for different reasons and I don't think one is better than the other. So in comparison the Mesa is a bit warmer , darker and sweeter on the highs than the Splawn, its also bit more forward in the midrange. The Splawn has a tighter lowend , the Traditional Mesa is not loose though don't get me wrong because that its more a trait of the recto cabs. So back to the Spawn it also has a bit more overall clarity and open top end, in general the Spawn cab could possibly cut a little better depending on what speakers are in it. They are both great sounding cabs , Ive also had Diezel , Bogner, ENGL and a few others to compare.
I also want to revisit the Bogner cab because I sold mine quickly , The speakers had been replaced by the previous owner and Im not sure but something seemed a little off but I did like the big and open sound it had , it had a certain rawness to it I liked. Surprisingly I also owned the Friedman JJ amp and I think the Splawn would sound great with it, I had regular greenbacks in my splawn for a while which works very well in that cab so the Creambacks also prob sound great in there. How much are they asking for the Spawn cab if you don't mind me asking ?