There is absolutely no difference in quality between the RRS and Wimberley plates. The are both top notch!
The explorer feature looks nice, however the only concern that I would have besides the extra weight, would be the stability of the camera position, as the center column top mounting plate, as it appears to be off to the side of the tripod (so the center of gravity is not over the legs), even when you're not using the horizontal feature.
Also check out the Gitzo Systematic Carbon Series 2 or Series 3; 3 section or 4 section. The prices on the Gitzo website are higher retail prices.
http://www.gitzo.com/news+%26+events...ipods/20183007
Note prices after rebate at B&H:
http://www.bhphotovideo.com/c/product/846201-REG/Gitzo_GT2532S_GT_2531_Mountaineer_6X_Carbon.html
http://www.bhphotovideo.com/c/product/846212-REG/Gitzo_GT3532S_GT3542LS_6x_4_SECTION_SYSTEMATIC.htm l
http://www.bhphotovideo.com/c/produc...4_Section.html
Also horizontal adapters are also available separately:
http://www.bhphotovideo.com/c/search?Ntt=feisol+horizontal+adapter&N=0&InitialSe arch=yes&sts=ma
I really hope I'm not confusing you or overwhelming you with information, as I'm not trying to talk you into any specific model. All of the models and brands listed are excellent!
I own the previous years model of the Gitzo Carbon Systematic 3 Series with 4 leg sections and I love it.
Rich