Hi LACarole!
I'm not familiar with differences in housing/rental costs between these towns, but maybe someone who lives in the area can help you with that.
One thing that is certain is that the Bartlett/Glen/Jackson area is definitely the more tourist-filled of the two. Usually the tourists are only in large numbers on the weekends... in the winter it's the skiers; vacationers in the summer; and leaf-peepers in October. Fortunately, it's much quieter in the spring and late fall.
Of course, that's not to suggest that the Bartlett area is swarming with people! The only place that you would encounter actual "traffic" is in Conway on the big holiday weekends. And one advantage of the Bartlett area is that you're literally in the heart of the White Mountains.
The Littleton area and the other towns you mentioned are slightly more off the beaten path. They're not quite in the mountains but are only a short drive away. You can definitely find the rural lifestyle you're looking for in all of the towns you mentioned, but the two areas are slightly different in this regard.
Bartlett, Jackson, Glen etc. are situated in mountain valleys, so there isn't much to the towns beyond the main road and the few side roads. But they sure are beautiful! Littleton, Bath, Whitefield, etc. have a bit of farmland and are generally less "commercialized" and tourist-oriented than the mountain towns, although Littleton is the largest of the towns you mentioned.