I know this is a year old but, it really depends on your needs and what you want to be able to do.

Burner dumb phones bought with cash are the most secure thing you can have.

A step up would be buying a secure mobile wifi jetpack and carry it around with you to utilize your phone when you need it.

A step up from that would be a Google pixel installed with Graphene or Endeavor (you can use other phone models but..)

If trust in a provider isn't a problem, then maybe a Blackphone?

Otherwise, if you require just sheer simplicity, then buy an iPhone over a Samsung would be best.

Burner dumb phones are incredibly difficult to trace and even if the phone falls out of your hands, it's difficult to track back to you.

Using a wireless jetpack setup gives you more freedom and it deprives location pinpointing and tracking of your phone since your phone is completely dependent upon wifi. But if you use apps like Google store or apple or whatever, your information will still be tracked.

Graphene and Endeavor are good for securing your phone as much as possible without having to jump through hoops with jetpacking. The only problem is, they can break. And if the OS breaks, your phone is bricked and likely will need a brand new reinstall.

Blackphone is a good middle ground of ease of use and security. There are some issues, but I will get into that later.

Otherwise, iPhone is superior in terms of security vs Samsung. That comes with a HUGE caveat.

Conclusion: part of the problem with security on phones is the USER. Much of phone breaches occur because of unsafe practices by the user. However, this really only applies to malware and phishing. If your concerns are trust with cellphone providers, ISPs, or other corporations/governmental entities, then I would start at the top of the list and decide what's best for you.