I had a Rockwood by Forest River prior to our current trailer. I was very happy with the trailer. At the time weight was a major factor in our decision as to what trailer we bought. After upgrading the tow vehicle, weight was no longer an issue and the lite weights were no longer in the running. The lite weight trailers serve their purpose very well, but if weight is not an issue then I woould look at conventional trailers. Lite trailers are not built as sturdy as conventional trailers, and as you have mentioned, fresh water, grey, and black tanks are typically smaller. Our Rockwood served us very well and was the better built lite trailers we looked at. Not to mention Forest River's customer service has been exceptional. They do have similar floorplans in their other lines as well. Some examples are the Sandpiper 301BHD and Salem 301BHD.
2005 F-250 XLT 4X4 V-10
2006 Wildcat 31QBH