Salesforce Lightning Design System (SLDS) vs Bootstrap - which one is preferred?

Responses I received from many other community members:

[Ratan Paul] LDS - Lightning Design System

[Nikhil Chowdhury] Both of them are equally good to use just the fact being that Lightning design system is more responsive and has pre-built classes to be used for compatibility on different devices.

[Ajinkya Hingne] Bootstrap anytime, but if we want to use one for Salesforce Visualforce pages, LDS should be used.

[Nandish Shenoy] From a dev perspective I would opt for Bootstrap since it has a much larger user base than SLDS. But from a user perspective would opt for SLDS since its supported by Salesforce. Also SLDS looks really cool.

[Yash Agarwa] SLDS is still in development for few features . So if you don't really need it, I would suggest holding on it for some time and using bootstrap.

[Bapu Rao Srigadde] I'm heavily using and developing lightning with SLDS. It is still evolving platform. For now you can use bootstrap but eventually you need to go back and update your implementation, when lightning is stabilized.

Thanks everyone for your participation. It really helps.