I'm with you -- keep the storm/screen door. Sounds as though it serves a purpose (light, air), and since it's the "back" door, you needn't worry about it detracting from the overall look of the exterior.

ALSO, when I'm bringing in say, several trips of bags of groceries, I don't have to keep closing the main door as the storm door will auto close and keep the bugs out. Do most of you have those 'two doors'??

First, does the back door face West or South? Is the main back entry door fiberglass?
Does that entry door get direct sunlight? If all 3 of these exist it is not a good idea to install a storm door. The heat build up could melt and warp the fiberglass door. Otherwise it will help with insulation, and protect the new door from the weather.

I love the idea of a full light storm over the front door so you can see it. Remember storm doors are basically for insulation so you have to ask yourself how important that is to you.
I'm with you husband and didn't put one on my back door. That is not just because I love a open doorway but here in Colorado there are not enough bugs to make it necessary so location is a factor.

I see a lot of people use these security/storm doors on there houses which look awful on the front but do allow you to leave the main door open in warm weather for ventilation and still have a locked door so no one will walk in. If security is a major issue in your neighborhood remember robbers kick in the BACK door not the front door so make sure your security door is the the rear for sure.