A lot of similarities between these two men...
Bret was made WWE champion in the shadow of the steroid scandal, and Funk was made the NWA champion due to politicking by his father. I suppose that neither were expected to be very successful, but they managed to prove their naysayers wrong. The difference was that Funk was a lot more successful at his peak compared to Bret. He carried the wrestling industry from 1969-1973 and became the NWA's most consistent drawing card since Lou Thesz in the 1950's. WWE struggled financially with Bret as champion. He never set the wrestling world on fire like Dory Funk did.
Both men were not known for their speaking ability. Bret often fumbled through promos, and it was clear by the 80's that Dory did not possess the type of charisma needed for weekly television like his brother did. But Dory had charm that Terry didn't have. It was the same type of charm Bret Hart had. Both could make any opponent look good. Better than they had been before. Dory elevated a ton of regional stars in his heyday, including Ric Flair in the mid 70's. Ric Flair himself has compared Dory's success as champion to that of Bruno Sammartino. He was that popular.
And lastly both men had their careers cut short. Bret was forced to retire due to complications from a concussion, while Dory was seriously injured during a car accident. The difference was that Dory was still in the prime of his career. The car accident was the driving reason as to why he was forced to give up the NWA world championship. Bret Hart had been champion in WCW, but his star power did little to help the ailing promotion. After dropping the NWA title, Dory later went on to win several top NWA regional championships, had a successful singles run in Japan here he was one of the few foreigners promoted as a fan favorite, and formed a successful team with his brother. He remained one of wrestling's most recognizable stars even in through the 80's.
Dory later became a booker and helped trained many wrestlers of the current era, including Kurt Angle, Edge, Christian, the Hardy's, and Mark Henry.
Vote Dory Funk. He was a much more successful champion and has done a lot more for the industry. Bret's legacy has been bloated by the WWE promotional machine. He was never anywhere close to being as good as Dory Funk.