A BH with lots of ventilation holes or the one with very little ventilation holes?
I will choose the lots of ventilation holes and not the little.
One obvious reason is that your BH air flow will be much better as compared to the little number.
I visited two BHs recently about one week apart.
The unit in Tanjong Karang was with very few ventilation holes and at Isab Kuantan with a lot of ventilation holes.
The Tanjung Karang BH while inside you can feel the stagnant air inside. No movement and you will feel as if your body is sticky and wet.
Within a few short minutes you will find some excuse to walk out for some fresh air.
If the BH is properly ventilated you feel rather cool and less sticky. Your stay inside is more pleasant and you have the desire to carry out your inspection.
Have a good look at the two BHs and try to count the number of ventilation holes on their walls: