If its anything like the other ad supported kindles, you can always turn off the ads in your account later. So if the s/o ones ship sooner, get those for now.
I ordered the wifi s/o on the first day. Had estimated date of 10/2. The next day I cancelled that order because of some reason and then reordered again with the same estimated date.
I am using a K3 right now and that was before the ads. So ads and touch will be totally new to me in my e-reader. I am a bit worried about page turning. We'll see.