Between the two there is a big difference:

One is a profession that can be a particularly dangerous way of life. Orders from above put you into place far from support, with limited resources, often in contact with hostiles on a daily basis. You're often left to fend for yourself with only what you have on you against overwhelming odds. Command structures often pit you against your peers in petty internal politics around rank. The pay isn't great, and those that stick with it for the long haul to make a lifetime of it often leave scared and mentally injured. It can be a thankless job in putting your life and health on the line to achieve the overall goal.

The other profession usually involves wearing a uniform and enforcing USA's geopolitical interests in other countries.