The analogy is apt, not just because of the size of the task that awaits the Exiles, but at nearly five stone lighter than his older brother Soane, not to mention an inch shorter, Hudson is very much David to his brother Soane's Golaith.
It will be the first time the brothers have faced each other on the pitch, although they've lined up alongside each other many times for Tonga and Hudson is looking forward to the challenge.
"I've always looked up to him," he said. "It will be interesting to test myself against my elder brother for the first time and I'm looking forward to it. The battle is on.
"I haven't spoken to him in the lead up to Saturday, but I'm sure he's looking forward to the game as much as I am.
"He really is a big guy, but that won't stop me from giving him a little challenge since I move a bit faster than him. Maybe Saturday will see David score another victory over Goliath."
However, Saturday won't be the first time this season that a London Welsh player has lined up against his brother. Full back Tom Arscott was pitted against his brother Luke, full back at the Exeter Chiefs, earlier this season.
In his third season now at London Welsh, since joining the club from Doncaster Knights, Tonga'uiha was instrumental in driving the club to promotion last season.
He finished last season as the Exiles' top try scorer in the Championship, with 12 tries, and came into his own in the play-offs, scoring crucial tries against Bristol in the pool stage, Bedford in the Exiles' semi-final win at Goldington Road and in both legs of the final against the Cornish Pirates.
Any concerns that Tonga'uiha might not be able to make the step up to the Premiership were dispelled in the opening two rounds of the season, when he scampered away to score in the corner against Leicester Tigers and five days later when he picked up a rampant Ugo Monye at Harlequins and marched him backwards.
Tonga'uiha, like Welsh, has adjusted quickly to life in the Premiership.
"I give it my best, I always have," he added.
"Knowing that I'm playing with and against top players in the Premiership pushes me forward, and I've taken my game up a notch.
"I'm proud of the results we've achieved so far as we're very new to the Premiership - every win provides confidence. We could have done even better but every mistake makes us even stronger for the upcoming games."
Two heavy defeats in the LV= Cup may have checked Welsh's stride after the euphoria of that late win over Bath at the Kassam Stadium but Tonga'uiha believes the Exiles can still upset the odds at Franklin's Gardens.
"Why not? We believe in ourselves and if we work together as a team then nothing is impossible," argued the centre.
"I'm sure the boys will give it their all."