Off Grid which generator to chose 10 kVA to 15kVA

Just finished getting pricing for Commercial grade generator systems, in the 10 to 15 kVA range

The YangDong YD485D generator  is rated as 17kVA 13kW Standby and 15kVA 12kW Prime
The YangDong YD480D generator is rated as 14kVA 11kW Standby and 13kVA 10kW Prime
The YangDong YD385D generator is rated as 12kVA 10kW Standby and 11kVA 9kW Prime
The YangDong YD380D generator is rated as 11kVA 9kW Standby and 10kVA 8kW Prime

The 4xx models are 4 cylinder the 3xx models 3 cylinder

They cost exactly the same

Which is a good thing, as price shouldn't be the selection criteria, so how to select, lots of advice say 2* your inverter size, but my 9kVA inverter system has 3kVA headroom for instant power, i.e. all those devices you shouldn't be using, like kettle for 3 minutes, power tool for 10 minutes, hairdryer for 5 minutes, microwave for 5 minutes, to allow for those I have a "headroom inverter" which supplies the power hungry users.

I have a constant power budget of around 3kVA and time of day dependent users which can take that up to 5.5kVA when the 2.5 kVA ironing session starts for 2 hours
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So what size generator, here looking at what three FXR3048E inverters can pull to charge batteries, the max battery recharge current they draw is 10 Aac each to charge with 40Adc each, so 30 Amps at 220V is 6.6 kVA
 
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The headroom inverter is catered for already because the inverters will just reduce power for charging the batteries for a few minutes OR draw from the "temporary use" generator standby power rating while users are reaching for the kettle and hairdryer 

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It comes down to

1) not oversizing and causing generator damage from insufficient load levels e.g. 40% vs 70% etc
2) fuel consumption (operating cost, smaller engine lower costs)
3) 3 cylinder vs 4 cylinder (I am trying not to think of this as my "new car" which is making me want to go 4 cylinder)
4) spare parts availability and service repairs which are fine with all 4 generators

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I know one thing, that when I need to run the generator it is because the batteries need charging (Dark days or failures or undersizing)
So being able to run load and charging is important, which in my case is 6.6 kVA plus 3kVA load plus 2.5kVA for ironing = 12kVA

The ironing won't always take place so when it doesn't I get 9.6 kVA loading = 60%, 70%, 80% and 90% loading on each of the four generators 
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One scenario is for emergencies if I have to bypass the inverters and there is no battery charging at all while the generator runs, this will not work well for any generator, but would be worse for the larger ones, however, I have a 5kVA generator for backup to power smaller loads only, without any battery charging.  I will arrange a transfer switch for that as well in emergencies, just in case the whole system gets struck by lightning, stranger things have happened, however I can't rely on the backup generator for long usage periods and will need to use the new generator as well in the event of a total disaster.

Which of the four generators should I choose, they all cost the same, I am thinking the 480D

Here is a video of the generator https://www.youtube.com/watch?v=1KQsMRrXoak