It depends on what's more important to you--ultra-portability or screen real estate. I have both the Acer C720 (non-touchscreen, Haswell processor, 2 GB RAM) and the HP Chromebook 14 (Haswell, 4 GB RAM), and they're both excellent. The C720 is the one I take to the cafe or on trips because it's super light, while the HP 14 stays at home as my utility kitchen laptop.
I'd stick with Chromebooks that have at least a Haswell Celeron processor, which is a significant boost over the earlier Celerons. The ones with the ARM-based processors have been noted in reviews to be generally slower. This includes the entire Samsung line (even the latest Samsung Chromebook 2), and the HP Chromebook 11. The newer Acer C720 with the i3 processor is even better, although it may not be entirely worth the higher price, depending on your needs. Acer's newest Chromebooks (the CB line) sport the new Nvidia Kepler processor, which is supposed to be a beast--but I haven't seen any real world reviews of if yet.
If you can get 4 GB of RAM, do so. My HP 14 is noticeably faster and smoother than the C720--they both have the exact same processor, but the HP has 4 GB while the Acer has 2 GB. Still, I'm totally satisfied with my ability to work on the Acer, with 5 or 6 open tabs including Google Play Music actively streaming.
The size of the SSD doesn't matter that much, since you'll probably be saving most of your work to Google Drive. So 16 GB should be fine.
Personally, I don't think a touchscreen is that useful on Chromebooks--at least not yet. I still find it unnatural to be moving my fingers from the keyboard to the screen and back again. The touchpads on my Acer and HP are very good, so I wouldn't see a need to use a touchscreen.
I recently tried a Toshiba Chromebook at a store, and although the specs are fine, I noticed the touchpad was not very good--it just felt grainy, and the function wasn't as silky smooth as the one on my Acer and HP. Also, the plastic of the Toshiba felt a lot cheaper.
You might want to look into the HP Chromebook 14, especially the one that comes with lifetime 200 MB/month of free T-Mobile HSPA+ data (which is what I have). It comes with 4 GB RAM by default, and the data can come in handy if you don't have a wifi connection and can't use your phone to tether. The 14" screen is easy on the eyes, and although the viewing angles aren't terrific, it is nice and bright, and the colors are more vibrant compared to the C720. You can occasionally find this Chromebook refurbished online for around $200-230, which is a great deal.
Good luck with your choice!