If you had 500,000 subscribers for a daily newsletter, what ESP would you use?

I know I can scale a profitable newsletter through Facebook Ads to 500K subs in a niche quickly. I’m looking at sailthru and mailgun. Obviously need dedicated IP. Would I just be better off going with campaign monitor or MailJet? I can do a lot with technology but have never interacted interfaces like sailthru or mailgun. Thank you so much for any thoughts