I'm going to say Vitali is the bigger, stronger and tougher of the two. Wlad is more athletic, fluid and has much better technique. That being said, I wouldn't want either of them busting me in the face.
Wladimir has more punching power in a single shot than Vitali, with either hand. It's been that way for years.
danny williams and corries sanders were 6 years ago....vitali jabs them into submission now... from 2000-2010 vital has fought 14 times 6 guys made it to rds 11,12 2 guys 10 rds 2 guys 9 rounds 3 guys 8 rds stopped by lewis in 6 stopped johnson in 2 stopped cruiserweight orlin norris in 1 so in 10 years....a guy that 6 foot 7 and 245 pounds....has stopped 2 guys before the 8th round...thats what i call some serious power....WOW :rofl