I am qualified to give an opinion. But not saying if you have any particular diagnosis. Only how to approach problem.
The two doctors are suggesting different diagnoses, one requiring (generally) no surgery....and the other requiring.
You can believe either one and proceed. Typically a biceps tear is far more common and you could play the odds game. But why do that if you are in doubt and you lift and wish to continue? Pectoralis tears happen during BP.
So....mri will easily distinguish between two processes and perhaps catch other stuff along with it that both doctors miss by examining acute injury and you could easily have multiple injuries and chronic issues.
I would vigorously dispute your 1k patient pay. Don’t know where you are and in this forum could easily be on Medicare. Outpatient mri centers must accept MCare payment rates.....FAR below 1k...
If not Medicare and you have big deductible,call the facility and ask for cash price. 500 tops in big city.
Look for facility with high power magnet....ie 3tesla. You can accept 1.5Tforyour purposes. Ask if musculoskeletal trained or experienced radiologist supervising and reading.
Make certain that your MD writes that likely biceps tear but possible pectoralis tear. Why?......because some deviation from standard shoulder protocol may be necessary and not standard, at least in most facilities.
Good luck.....are you worth 500$, given the very different consequences of the two possible injuries?
PS.....amazingly if it were your dog at vetyou would pay at least 1k for care of nothing burger concern, gladly. But I’ve been around a long time and people just hate to pay for their own care. But don’t fret....it will someday all be FREE.