UK FPS vs BB Weight

I have recently acquired my first Airsoft gun. Rummaging through posts here, people seem to universally suggest that BB weight trumps FPS when considering range, accuracy and ability to cut through foliage.

In the UK, there is a Joule limit of 1.2. To keep under this limit, my .30g BB travels at around 290fps. A .25g BB would travel at 320fps.

Is FPS difference between weights still not a significant thing to consider? Is it still better to simply opt for the most weighty BB?

Thanks