2720SD or 2720SL

My husband and I are retired and currently camping in a loaded '99 Coleman Niagra. Although we have been very pleased with it, we are hoping to upgrade to a Trailmanor. We had looked at new units and found them out of our price range and were so glad to stumble on your website with its wealth of info. and opportunities to buy previously owned trailers. We have narrowed our preferences to the 2720SD or the 2720SL since we do not need 2 permanent beds and would like some input from those of you who own either of these. Please let us know why you chose, like, or dislike these models. In looking at pictures, it seems that the heater vent on the 2720SL is on the front of the sofa? Is this uncomfortable for someone sitting on the sofa? We appreciate any input you can give us.