Found this post on a Flightsim.com forum, after doing a search:
http://www.flightsim.com/vbfs/content.php?13716-Review-Sim-Physics-X
@MikeSim68
Tested Accufeel in the past and Sim Physics X now , I can say that comparing both programs is like comparing day and night. Their only similar function is the sound and visual 3D cockpit effects on some weather conditions. But that's where any comparison ends... They are totally different products...
(And by the way they - Accufeel and Sim Physics X - work perfectly together with some clicks here and there...)