After using either one of the illuminated e-ink devices, you may find it difficult to go back to the old e-inks. Font support is more flexible on Kobos but the novelty wears off after a while.
I went for the Kobo because I didn't want to be tethered to any single vendor, their desktop software or infrastructure. Kobo tends to be quite "open" and where they're not, there are ways to make it so.
http://www.theregister.co.uk/2009/07...4_from_kindle/
I think the screen on Kindle Paperwhites are a slightly better in terms of aesthetics however.
Large number of books on the reader is difficult to thumb through. I prefer to keep the bulk of my library on my PC. Calibre is good for this. Since the devices have to be charged, connecting USB cables never poses much of a challenge.