We have had a fifth wheel with two AC units and one with one AC unit. I much prefer the two AC units because I like it cool when I sleep. My body still produces too much warmth and it's awful to have to go to the living room in the middle of the night and stand under a vent just to cool down.
That being said, we camp in the mid-Atlantic or South for most all of the summer. It is usually still hot/humid at 10 pm or later and we NEED the 2nd AC. When we went north into Maine, I did not use the AC at night at all. It got down into the mid-60s and I had the windows open with the night air blowing through it. It was wonderful!
The 2nd AC unit does make the bedroom not only darker, but harder to cool down if the AC unit is not on. With our fan, it had a white cover that allowed light to illuminate the bedroom in the mornings (sometimes too much) and with the 2nd AC, there is none of that ambient light getting into the bedroom. Our windows, the two by each side of the bed and one on the entry side do not give us much ventilation. For those times when the 2nd air is not needed, I have a small fan that hooks with a clamp to my bedside table and blows air on me.
I guess most of this will be be whether or not you will use it with where you camp. If you do not plan to head south to the hot/humid areas, then go with only one. If you have plans to head south at any time, get the 2nd AC. If you are worried about resale value, get the 2nd. Even if the things costs the same whether you have the 2nd AC, you may regret having it to block the light and not having a fan.
If you can get both the fan, plus the 2nd AC....go for it!