Which type of tie is best to use inside the PC to gather all wires inside the PC?

Both work but we all know that zip ties is the right way to do it.

Exactly.

How often do you plan to mess with the insides of your PC?
If it's rarely or never then yes zip ties.
If you're often going to be tinkering inside you might prefer twist ties or Velcro straps so you can undo them easily without having to cut and replace zip ties all the time.

Seb

Velcro straps have the added benefit of not having a conductive wire inside them like twist ties do.

I prefer Velcro straps, because they are reusable, and look better than twist ties. They do cost the most of all three, though.

Ties will enter in tighter spaces and depending on your needs there are from very small to very big, they are very cheap, personally i prefer this. I do use velcro straps sometimes, depending on the space i have, but i do prefer ties.

Thanks for your valuable replies guys.

Zip, 100% poly

Twist tie does (previously mentioned) have evil metal core.

I use heavy duty zip ties but I insert the end in up side down so that they don't ratchet/lock into place. Being heavy duty means that the tension is enough to keep them tight but when I need to reroute a cable, all I have to do is loosen the zip tie, do what needs doing and tighten it up again.