Normally I'd agree with you, but the make up of the games means 2 draws works very well.
If it's 3 points, I'd much rather they came against Exeter. Not losing Saturday is the most important element of the week.
2 draws intuitively feels better as it denies both opponents the 3 points but (assuming your key goal is auto promotion not winning the championship) then a win & loss, even if the loss is to Exeter, is mathematically superior.
Compared to 2 draws, if we beat Colchester and lose to Exeter then:
We lose 1 net point relative to Exeter (they gain 2, we lose 1 and gain 2)
We gain 2 net points relative to Colchester (they lose 1, we lose 1 and gain 2)
We gain 1 point relative to Plymouth, Crewe, Northampton, Bradford, Cheltenham and Forest Green.
Overall that is far better for us in terms of finishing in the top 3.