The only cases where I'd install different brake arms are:

• The existing ones are corroded or blemished or the wrong color (if you're trying to color-match components)
• The existing ones are of the stamped steel variety and notably flexy or don't operate smoothly
• To install longer arms

There are several lengths of linear pull brake arms...as short as about 80mm and as long as about 120mm. Usually, the shorter arms are paired with short-pull levers and the longer arms are paired with long-pull levers, but this is not universal. And I've found that you can really tune the feel and power of the brakes by changing the length of your brake arms.

We have a 2015 Raleigh Alysa (similar to a Trek FX series) that came with Tektro BX-1 brake arms (these are the short arms usually intended for road or BMX applications) paired with typical long-pull brake levers. In this case, swapping those 85mm BX-1 brake arms out for 100mm Avid Single Digit 5 linear pull brake arms (using the same brake pads) made a nice difference in braking power, because the cable from the lever had more leverage over the brake pads. This is probably how the bike should have been setup originally. I suspect the long-pull levers with the short BX-1 arms was a move designed to reduce braking leverage for a bike presumably intended for a novice rider to prevent an over-the-bar accident...perhaps similar in concept to using a brake power modulator (which this bike did not, and does not, have).