As a doctor, you will be able to pay off your loans and live comfortably. Very few doctors earn less than $150,000 (before taxes but after malpractice) without making some deliberately career-limiting choices -- eg. working part-time. If it's important to you, you will be able to make considerably more by specializing and/or choosing your practice carefully.
As a software engineer, MBA-type, or lawyer, if you're really good at your job and really good at all the other stuff you need to do to get ahead (company politics, sales), you will probably be able to make the same. If you're not so good at either the work or the schmoozing, you will make considerably less. If you're reach CEO, law partner or land in a successful tech start-up, you could eventually make much, much more. Until then, though, you will almost certainly have to 'pay your dues', work your tail off, most likely at some point, work for an idiot who is much less intelligent and much less capable than you, put in LONG hours, eat the proverbial poop hot dog on occasion, and do soul-suckingly boring, frustrating or ethically-grey work. There are upsides, of course. But if you're considering the downsides of medicine, don't overlook the downsides of the alternative.
Most importantly, look at the career satisfaction, the life satisfaction each option provides. Making money is only one measure of the successful life, and I would argue, not the best one. The whole purpose of earning money is to allow you to live the kind of live you want to live and provide a good and secure life for the people you love. For that, you need 'enough' -- not 'the most'.