bxcc, I know the Workswell WCB-M-078 and CS-527 look slightly different but when requesting information from Peter and from Workswell, I received the exact same spec sheet so I would expect they are both the same. Either frame works with 27.5+ or 29+ tires.
The DengFu frame looks like the Workswell and Carbonspeed frames but had different specs listed. However, the pictures on the websites are exactly the same. Most likely all three of these are the same frame.
I am not sure what the spec sheets they sent you contain but I can guarantee that the WW frame and the XMCarbon frame are different. Their forks are the same though. Here are some differences that stand out in the pictures (Peter has posted some nice pictures of his on FB).
-Seat tube - WW is curved back near where the drive side CS connects, XM is straight from BB to top.
-Drive side CS - WW is again curved and the XM one is straight.
-Top tube - WW has a bend just in front of the seat tube and the XM top tube is completely straight.
-Chainstay length - WW is adjustable from 440 to 425 and the XM frame is fixed at 430.
-Seat Post - WW is 27.2 and XM is 31.6.
I haven't seen the spec sheet that Peter is providing but the pictures look identical to the Dengfu frame and they have a spec sheet on their site. From the measurements that I have taken, the WW spec sheet is pretty accurate.
With all of that being said, for me there really isn't one that is "better" than the other. Just slightly different. I guess it probably boils down to price and personal preference on looks.
And for anyone that is interested, here are some links.
Workswell / Sobato
http://www.workswellbikes.com/web/view/161.htmlXMCarbon Speed (Peter)
http://www.xmcarbonspeed.com/Productinfo.asp?f=1414Ican 29+
http://www.icanbikes.com/html/MTB/29ER_frame/317.html#bk_desc_tabIcan 27.5+
http://www.icanbikes.com/html/MTB/27_5ER_frame/330.html#bk_desc_tabDengFu
http://www.dengfubikes.com/MTB_FRAME/195.html