When I was researching for my bike it came down to your exact options, in fact I started off with the mindset that I WOULD purchase the Fat Bob. I had never even heard of the Triumph Storm at the time. The first time I laid my eyes on the Storm though it felt akin to locking eyes with a very attractive girl. From that point forward I coudn't get the storm off my radar, you see the Harley dealer is 3 miles from my house and the Triumph dealer is around 70 miles from my house. But every time I went to the Harley dealer (which was a lot) I kept finding myself thinking about the Storm.
Everything about purchasing a Storm from a time standpoint was very inconvenient for me, but if I don't buy what I truely want I will have buyers remorse. I have absolutly no regrets with my storm.
A buddy of mine has the 2011 Hayabusa, I believe they are the fastest production bikes made (stock out the door). The Storm will be a much different ride, make sure you pick the bike that makes you feel good. Coming from a sportbike the Storm seems like a more natural switch than the Harley Fat Bob (ride a Fat Bob and you will FEEL why that is)
I have nothing bad to say about Harley or even more to the point a Fat Bob. With Harley you will get much more chrome, service convience and lets face it Harley is THE most known crusing bike from a branding standpoint. The Fat front tire on the Bob looks great IMO but hinders your cornering ability.
The Triumph Storm handles much smoother at high speed and corners, and the midrange torque on the Storm will make you smile every time you punch it out of a turn.
I live outside of Detroit, MI. and most of the people around here ride Harleys. Six of my buddies at work have Harleys (which is why I was initially so set on getting one), but I catch them all the time looking at my "woman". In fact Harley guys always check out my bike, most saying something to the effect of, "I didn't know Triumph made such a nice looking cruiser"
At the end of the day it all comes down to what bike makes you FEEL good, and if you pick your bike based off that you can't go wrong.