What really is the difference between the two? I see that Watches for sales have more "dealers". either one of them more safe to deal with?

 

Dealers are more for profit as that's a job for them and private is more for the collectors to flip watches to buy their next.

Depends what your after new or vintage also, as most vintage are in the private section.

You can read the feedback from both in the sellers review section

https://omegaforums.net/forums/watch-seller-profiles/

It still pays to buy the seller and do your due research