Not necessarily. Let's use Coriolis' specs as an example.
We'll ignore the Huge mount as it is a shared element.
1 Fixed Large Pulse Laser is 18.1 DPS
1 Fixed Medium Pulse Laser is 12.1 DPS
1 Fixed Small Pulse Laser is 7.9 DPS
Mamba; 2 FLPL + 2 FSPL = 52
FDL; 4 FMPL = 48.4
The Mamba has a tiny bit more 'raw' DPS due to the way damage increases by mount sizes. Once you get into various loadouts, armour hardness, armour piercing, and so on, the difference starts to evaporate pretty quickly.