There can be no guarantees of the product you'll get on any route because of the occasional equipment problem and resulting aircraft substitution. Seatguru.com and seatexpert.com will give some information about the scheduled aircraft and seat types available but obviously you can't see the product and there aren't specific reviews. You can find some reviews here at FT in the trip reports forum, http://www.flyertalk.com/forum/trip-reports-177/, and there are more at airliners.net: http://www.airliners.net/aviation-forums/trip_reports/. You may not find reviews for all of the specific products on your route, but these steps may give you some idea of the products being offered with the proviso that you still can't guarantee the product you'll get until you actually get onto the plane.

In other words, despite your best efforts, buyer beware remains applicable.