I am a ground the neutral kind of guy or at the very least resistive grounding but there are other things to consider. Is this an emergency generator or standby for a building that works on a power failure? Is it a power supply for an industrial operation? Both of these may require an adjustment in the grounding of the generator. If this is used with a floating ground then you are also going to need ground detection lights so someone will know there is a ground falt. I like to see a breaker installed at the generator so the generator does not have to work on a fault but not grounding it to protect the generator is a dangerous reason to float the ground, because if you get a ground fault on a phase then another the explosion will be just as loud and damaging as if it faults to a solid ground.
Is there a transfer switch involved? open neutral or closed? A 3 pole transfer switch would require you to lift the neutral from the chassis in the generator so as to prevent a second ground on the buildings service.
There are a few things to consider before you decide grounded or open.
