I don't use an alarm. In fact, I know people who just leave the F6B key in the ignition wherever they go.
The F6B - due to poor marketing, etc - isn't considered a "prize" bike.
And? If someone REALLY wants to steal your bike, they're gonna do it. Doesn't matter how many chains, alarms, or locks are on it.
I've had Isleen all across the country, and while people give her a second look, that's about it.
I'll leave her parked in any reasonably lit parking area without worry.
But like oil selection, whatever you are comfortable with will definitely help you sleep better.
Cheers,
Steve