The quality of the materials was stepped up in the 03+ seats for Bonnevilles. The stitch pattern is the same that was first seen in the Classic Aurora, and I have a ton of baised literature about how superior the design of those seats are. From experience they are a bit more soft (in the Classic Aurora) then the 2nd gen seats, which then made their way to the Bonneville in 03. However I do not know if the Bonneville had the lumbar adjust option.
The advantages: better material, better longevity, look great
The disadvantages: lack of bolstering side support.
Question to Boost who complained about the seats in Cfootes Aurora....did you adjust the lumbar properly? I've sat in the 2nd gen Aurora seats and they are not as nice as the Classic seats. I've found that proper lumbar (both upper and lower) made a world of difference.
Being 5'8" I really didnt like the seats in my 94 SSEi when I had it, despite the side bolstering. The Aurora seats were just so much more inviting once the SSEi was gone, and seemingly more suited for my height.
Diamond White Classic Aurora - Back on the Road
Galaxy Silver Grand Prix GTP CompG - Soon to be mothballed