I have both a JRB Sierra Sniveller and two EE Revelation X 20 degree quilts. I had bought the JRB quilt early last year for myself, and bought the two EE quilts for my sons just before our JMT hike last year in late July. Both are well made, although I did have a seam separate in the Jacks R Better quilt on the JMT and had to field repair it with super glue (holding so far). This with my sons being much tougher on their quilts than I am, often waking up next to their pads, partially on the dirt/rocks when cowboy camping, and in a complete 180 from their original sleeping positions. The EE quilts are built tough yet still very light. I give the EE quilts the edge there.
Regarding the poncho feature of the JRB, I don't hike with it as a poncho, but it is nice on those cold mornings when you have to get up for something. Its nice just to slip your head through the hole and stand up. It keeps you warm until you can get your hiking clothes on, and even for a bit after that until your clothes warm up. As others have mentioned, I wouldn't want to take the chance of damaging the quilt by lounging around in camp with it, but I could see using it for specific ultralight trips where everything is minimalist such as in the Adventure Alan link above. Its also nice to know that you could go to it as an extra insulation layer should things turn out to be a lot colder than expected. The EE quilt could be used like that as a wrap also, but the JRB makes it much easier.
I just bought the regular width/half taper with overfill from EE. One was a long (in case I wanted to use it) and one regular in length. I'm 6'3, 200 lbs and even the regular is long enough for me to use, although I prefer the long. Width wise, both are fine and easy to sleep under, but you might want the wide if using it to augment a sleeping bag.I'm a side sleeper as well, but even at regular width with both the JRB and EE quilts, they conform to my position and the width is fine.
Service was great from both. Tim was quick to answer email questions being that I ordered the quilts barely a month from our hike, and the delivery time on the website said to allow 3-4 weeks. He assured me that the quilts would be delivered in plenty of time and they arrived about 2 weeks after I ordered them. No problems from JRB, they were courteous as well.
If buying another quilt, I would likely buy the EE, mainly because I feel its a better value being the less expensive option. But I do like the Poncho feature of the JRB quilt and do use it as such under the circumstances I just mentioned.