Different trails for different… uh, mountain bikers?
I'm the exact opposite, I find the trails at Big Creek to be a bit boring, but I'm not really riding the free ride area, so that probably is the difference. Outside of the FRA, I'd say the trails are way less technical than the ones at Blankets (and I don't consider Blankets to be very technical) but you're probably including the FRA.
The signage at Big Creek also drives me crazy, most of the signs only show part of the trails with no indication that there are additional trails; I guess they don't want noobs to the trails knowing about the FRA? I'm riding around in circles thinking, "I know there is more out here." And then some signs show a trail in one color and then you come across another sign and it shows the trail in a different color. Most of the trails seem really short but I guess if you ride there enough, you know how to string them together and how to find all of the trails. My son does enjoy the pump tracks; I'll leave him there while I search out the trails off the maps on the parking lot side.
Quell Hollar doesn't seem to be much, if any, more than Turbine at ORM and Turbine is rated an intermediate so not sure what is up with that. Quell Hollar seems to attract a lot more kids, easier to get to from the neighborhoods I guess.
The XC area should be 9 miles if you do everything at Big Creek. They've done a much better job with signage in the last 6 months or so, but it is easy to take a cutoff and miss part of the trail system. Your best bet is generally to stick to the outside perimeter of the trail (so stay right on TThSa, left other days), that'll get you to 7.5 miles. The remaining 1.5 is Troll, which starts at the upper lot and cuts down the center, should add another mile to mile and a half. It's not technical in the Pisgah sense, but I've found it moreso than other trail systems in the area.
The freeride area is mapped and marked, but it's a bit more hodgepodge once you get there. There are 4 or 5 main trails, but some of them (Lunch Line in particular) have a number of different unmarked trails branching off of it. The main ones are labeled, though.
It was originally easier to find the FRA, but people were coming out and climbing up Pine Hill, then going down unprepared for some of the features and getting hurt, so they tried to separate them a little more. You can access the FRA using an access trail near Pine Hill (just before on the left if going MWFSu, just after and on the right the opposite day). There is a lot there, best bet is to go with someone that knows them. The main trails are Gully, Honor Roll (which feeds into Gully), Slalom, Sender's Row, Lunch Line, and Typhoon.
With the exception of Typhoon, the main trails aren't overly technical. Gully had a few root features at one point, but they've since been filled in. The more interesting portions branch off of Lunch Line into one of several rocky sections that get somewhat steep. On Typhoon, there are a few more rock features including a 4ft-ish rock drop with a chicken line to the right. Again, it's no Pisgah, but it's the closest to anything I've ridden around here.
It's also closed much less frequently this time of year. I live a mile away and can count on one hand the number of times it's been too wet to ride out there in the last year.
I'll have to revisit Blanket's, it's possible I missed something. I've been a few times, but I usually just do ORM if I go out that way.
For Quell Hollar being rated black, I expect that they do that since people tend to get a little braver on trails like that and get hurt. I know a few months ago someone was carried off in a stretcher doing runs down it. There are also a few gap jumps, or were the last time I rode it, so I expect that plays a part. They rate all the trails in the Big Creek FRA as "expert only", despite several of them being primarily smooth, I think it's primarily due to the jumps and people potentially injuring themselves, although there are one or two there I'd put in the expert category for sure.