As I am fat and have both a Kona and a Cannondale, I feel like I can add something.
Both are great bikes. you can make either one work for you and you will be fine, but it depends on what you want to do.
The plus of the Kona is that it is a beast.It will take the abuse you can dish out and beg for more. I started out at 350 and my Kona Jake took it all and my gear.
Mine also has a good hill climbing gear which is great when you are starting out.
The down side is that it is speed limited. These days I figure about 9.8 MPH over any distance with the Kona vs 11 with the Cannondale. But back when I was in shape I could average 13-15 MPH on a Cannondale CAAD8 vs 10.5MPH with the Kona. for your commute that means it will always be around an hour on a Kona, but could get to be 40 minutes on a road bike (or less if you hoof it)
Cycle cross bikes really max out around 20 MPH even down hill for me. Past that the resistance from the wind and tires is just too much.
If I were you I would start with the Kona, despite all I said. Its more forgiving and less likely to kick your ass when you make a mistake. Plan on driving in Monday with clothes for the week (you will want to change, trust me. Some deodorant might not be out of the question but YMMV on that one.) Bike Tuesday-Thursday and Friday bring all your stuff home via car. Start saving for the road bike though because if you are like me after 3 months the Kona is going to be pushing its limits and you will want to go faster. Figure that at saving $30 a week on your car by not driving it you can afford a $1000 bike if you keep it up for 33 weeks; sooner if you include reduced medical expenses and a better attitude from being in shape. I would just say when the Kona drives you nuts get a faster bike.
The make racks for bikes without eyelets but personally I like to keep it light I bike with a water bottle, tool kit and a mini bike pump. maybe a Lara bar just in case.