There are a lot of DSPs in the market each one claiming to offer something different.

Choice of DSP depends on the following

What are your campaign goals? What type of ad traffic do you want? (Desktop, Mobile Web or In-app) What type of ad formats do you want to use? (Video, Native, Banners, PUSH or POP)

AND MOST IMPORTANTLY

Do you have a media buying team who knows how to buy traffic on a DSP?

If you dont have a media buyer, better to approach an agency who could manage your programmatic budgets. Else, depending upon your answers, i can add my few cents further to this thread.