There are various posts re the "wasted" space in the Kobo forum, the most recent thread is this one:
Will the footer issue ever be fixed?
Yes the first generation Nook Glowlight has an SD card slot, but the difference in screen quality (and to a lesser extent, the speed) between it and the Aura HD is quite substantial.... though to be fair, that might not bother you. Plenty of people are happy to save money and pick up an older Nook cheaply, I'm pretty careful with my money but in terms of quality the only competition for me when I was upgrading was between the Paperwhite and the Kobo Aura/Aura HD. If I'd been happy to get a non-lighted reader, the Sony T3 would have been there too.