I have a Challenge Hurricane, but not an SL, which is notably (13 lbs.) lighter, I believe. I suspect that the Hurricane you are considering has brakes which are called “disc” or “hydraulic” or something. That is to say, a certain brake fluid (e.g., Magura) needs to be applied every few years or so. While this type of brake is considered to be superior, unless you yourself are able to “bleed” (that’s the word they use) the brake, you would need to live near a bike mechanic who can, if you opt for the Hurricane. I do commute 8 miles round trip on my Hurricane (and have done so for almost 1.5 years), but let me say that in traffic I am a little bit more comfortable being on my Bacchetta Corsa, as sometimes I worry about whether drivers can see me on a low racer such as the Hurricane. Unlike the Giro, the Hurricane does have rear-wheel suspension, but I am not sure how much it helps make the ride smoother (which isn’t to say that it doesn’t help, I just don’t know how much it helps). I am able to get fenders and a rear rack on my Hurricane. The Hurricane’s seat doesn’t permit one’s back to have access to air, so after riding long rides (and on March 15th I went 135 miles), one’s back can become quite wet through perspiration. (Though this doesn’t bother me). The Euromesh seat of the Giro likely permits better ventilation. The Dutch very much like to protect their bicycle chains from the elements, and the tubing that the Hurricane’s chain goes through makes it much less likely that chain lubricant gets on one’s pants. Bacchetta is located in Florida and has an online users’ forum with regards to their products, while it may be harder to successfully communicate with bicycle company based in Holland. One thing I like about my Hurricane is that the seat is so long that it can essentially act as a headrest (neckrest?). I’m not sure how many chainwheels (the crankset) the SL you’re considering has, but my Hurricane has only 2, and if I want to go up the 11 percent grade hill not far from my home, I shall have to use my Corsa. Like the Corsa, the Giro has 3 chainwheels up front.
All in all, I personally would go with the Hurricane SL. Intuitively (and my intuition could be wrong), it seems to me to be faster, more stable, more comfortable. If you opt for the Hurricane, you can get a flag for the back of the bike (as I did), for greater visibility.