I hope to soon start commuting to work via Bicycle and I have my choices for a bike narrowed down to the following two:

Trek 7.3 FX - https://www.trekbikes.com/us/en/bikes/2008/road/fx/73fx/

Specialized Sirrus - https://www.specialized.com/bc/SBCBkModel.jsp?spid=32215

I've tested a lot of bikes and these have come up as my favorite, but I cannot really tell the difference between these. Price points are roughly the same so I'm looking for any other factors to make a decision. I'm a newbie to "serious" bike riding so I'm looking for advice from anyone with a little experience.

Thanks In Advance!

Most bikes at a given price point are very similar in terms of specifications. The Sirrus has higher stock gearing. The Trek is a bit lower. If you're in a flat area, this means the Trek might feel a bit slower. In a hilly area or carrying a lot of stuff on the bike, the Sirrus would feel slower. Gearing can be changed after you buy a bike, so it's not a huge deal. And as you get stronger you might find you want different gearing (and that doesn't always mean higher... I'm a much stronger rider than I was a year ago, which means I'm carrying heavier loads, hunting for steep hills and want good low gears)

I'd make the decision based on which bike is most comfortable. A good fit means you'll ride more and longer, so you'll get more out of the bike.

Make sure you've got room in your budget for extras. Often extras work to eliminate the "what if" barrier. What if it rains, what if someone tries to steal my bike, what if I'm out late... Locks, fenders, racks, lights, helmet... all of those can be useful. Even if you don't plan to ride at night, lights can be helpful. They make it easier for people to see you in rain or fog. Fenders do the same kind of thing. If a skunk stripe on your clothes will keep you from riding, fenders are a must.

Most dealers will swap out a cassette at the time of sale for little or no cost. I am notorious at my LBS for swapping parts
when I buy a bike. I routinely trade in the wheels and tires and cassette. I have also been known to change out shifters and saddles. Trust me, they aren't losing money doing this.
If you want to ride around hills, get a 34T bailout gear. The day will come when you
are fully loaded, tired, and cranking up a hill. On that day you will think kind thoughts about me

Test ride a few bikes, if one feels better to you, get it.

I have a Sirrus Comp, which I like a lot. There are two things about it that aren't so great, but they're really only problems if you're going touring. These are:

1) It has a carbon fork so you can't attach a front-rack. However, it comes configured so it's
trivial to add a rear-rack.

2) There is a shim-like thing where the stem connects to the handlebars. The problem with this is that many accessories that go on handlebars don't fit on the shim. This is a problem with most of the handlebar bags I've seen. Plus, my Mickey Mouse bell doesn't fit.