Let me clarify that Doom Emacs is not "same as Spacemacs, but faster". This is probably one of the biggest misunderstandings about these two Emacs frameworks.

You can end up with a similar feature set using any of the two, and yes, Doom Emacs will probably be a bit faster, but they are not entirely equal. The user experience is different, one easy example is that while using SPC as a leader key is a feature in both, the keymaps are quite different.

My recommendation would be to try them both: they are easy to install, and uninstallation is as simple as removing the Emacs config in your user directory.