Vitali. Vitali would take it to Wald, Wald can't take it to Vitali. Vitali is tougher and has the chin.
Vitaly has 2 'primes': before and after retirement. I think 'before retirement' Vitaly would loose to prime Wlad because he was not experienced enough and would walk into a monster punch. However, older Vitaly would take Wlad to deep waters and TKO him.
I beileve Vitali would beat the hell out of his kid brother. First solid right hand & Wlad wouldn't even stay vertical like Adamek did in the 2nd round vs VK.