You own all three or you're deciding which of the three to purchase?
If you own all three, then I'd try all three and choose the one you prefer.
Personally, I think Sovtek 5AR4 suck.
I have never heard of Ruby, and I have never listened to a JJ 5AR4.
I'd try to find a Dynaco/Mullard or Fisher/Mullard on E-Bay. They're the same as the Mullard branded 5AR4, but they sell for less.
If you own all three, then I'd try all three and choose the one you prefer.
Personally, I think Sovtek 5AR4 suck.
I have never heard of Ruby, and I have never listened to a JJ 5AR4.
I'd try to find a Dynaco/Mullard or Fisher/Mullard on E-Bay. They're the same as the Mullard branded 5AR4, but they sell for less.