Source SDK or NO Source SDK

What is everyone's opinion on the Source SDK? Use it, not use it, post opinion and back it with your reasoning. Referencing internal cheats more than external but not discriminant.

My Opinion:
The SDK has a lot of useful tools but (I) lack(s) the information to get started. Looking at many of the github repositories and others, it seems like it would be useful but I lack documentation for it. Regardless, I would like to get to know how to use the tool for it seems like a powerful thing to have.

I'm also learning on how to use it correctly. I enjoyed internally without the sdk aswell. I prefer coding without the sdk, because i personally like doing everything myself and your project is a lot cleaner. but it seems like using the SDK just goes way faster + more examples of how to do things with it.

That's my opinion

EDIT: If you're looking for sdk usages, i really advice you the Chameleon source or MarkHC's Simple Base.