The Dutch boss has managed both players at Craven Cottage and White Hart Lane, respectively, and believes the Belgian is more talented despite recent praise for the Wales winger
The Dutch coach reluctantly sold the 25-year-old Belgium midfielder to Spurs for £15 million last summer and his high-intensity displays have been integral in getting his new side to third in the table.
And Jol - who has managed both clubs during different spells in England - believes that despite Bale being a hot favourite for various Player of the Year awards, Dembele is the true star of Andre Villas-Boas' side.
"We wanted to keep Dembele," he told reporters. "You can give him the ball and he won't give it away because he is too strong - even if there is no time and space.
|COMMENT: How quiet man Dembele has filled the Modric void at Tottenham|
Spurs' win rate with Dembele in the team is an impressive 68 per cent, winning 15 games while drawing two and losing two games - but without him the win rate plummets to 14%, with one win, two draws and four defeats.
While Spurs narrowly qualified for the quarter-finals of the Europa League after going through against Inter on away goals (4-4 agg) at the San Siro on Thursday night, Jol doesn't believe tiredness will be an issue for his former club on Sunday.
"They have a big squad," he added. "If you rest five or six players, like they did at Inter, there is no problem."