Another difficult choice - Use camera built-in flash or not?

Hi Guys,

I have been asking these weird questions time and again but can't help it as I am getting more curious and inquisitive to delve deep into photography. I am not even a P of Photographer but these are some of the snaps I took in London's Science Museum.  

The question which really engrossed me after watching these pics was whether to use camera flash or not? Have a look -

Clicked using flash of Panasonic FZ5

 Captured using the natural/artificial light as seen at the museum

Another angle of the amazing and colorful shapes - taken without flash

 This one is using flash

There are several colors in this picture which gives a unique effect.

Do comment about what are your thoughts on the same.

Cheers!!!

Pictures taken using Panasonic FZ5