I bought my artificial tree when I lived in the city ($40 at Value City before Christmas!) over a decade ago so it was definitely cheaper than paying $70 for a tiny real one in the city each year.
Now that I live in the country it looks kind of sad next to the towering pines outside my window. I also live close to several Christmas tree farms. They are always planting new ones and are very responsible with everything. All the trees they plant help to filter the air and increase oxygen as any tree would. Plus, we can easily recycle ours into mulch.
I have wanted a live tree with roots, but I have a hard time keeping houseplants alive here (low light and dry air), and it usually takes several months for the ground to thaw enough to plant the trees here.
If a tree has to be trucked a really long distance and then ends up in a landfill then it's definitely not greener, but if it's grown locally and can be used as mulch, I think that's better for the environment.
Of course, if we already own artificial trees, we shouldn't throw them away and get a live one to be green! We should get as much good out of them as possible.
"...for the happy heart, life is a continual feast. Better to have little, with fear for the Lord, than to have great treasure and inner turmoil." Proverbs 15:15b-16 NLT
The pessimist sees difficulty in every opportunity. The optimist sees the opportunity in every difficulty.--Winston Churchill