Both. 1.5/3 T is standard, >3 T machines (such as 5 T from United Imaging) are becoming more popular (and affordable) and at the same time ultra low field ones keep improving and now they make some things that were impossible before now actually doable such as bed-side MRI (not in clinical practice of course, but there was nice engineering proof of concept with ultra low field MRI machine that could be powered by normal power outlet).

Research is going up; clinical is going down.

The idea behind the recent boom in low-field stuff is that you'd like to have small/cheap machines that can be everywhere and produce good-enough images through smarts (algorithms, design) rather than brute force.

The attitude on the research side is essentially "por qué no los dos?" Crank up the field strength AND use better algorithms, in the hopes of expanding what you can study.

It's trying to, but "low" is still 0.5-1.5T.

I know nothing about the "industry" of MRIs, but from the physics side, (everything equal) more Tesla is better - at the end of the day, harder magnetic field gets you a stronger signal