We have 2005 Vectra 40KD since 2010, full-timer RVers since 2011. We are very pleased with our coach.
Suggest you check that 34TD for fiberglass decontamination, which is as an indicator of past water damage and possible mold. Our windshield channels did develop some rust, but we had them painted with POR to avoid further damage. Otherwise, if it looks in good condition upon close inspection, it probably is in good condition. There will be a regular series of issues with any 15-year old coach, even with a well cared for Vectra, but diligent maintenance will head off any emerging and future repair issues.
The visual feel of interior on a 34 TD is about the same as our 40KD. However, the 40KD has significantly more basement storage room for full-timers. The up side of the 34TD is that it can get into State Parks etc. that do not have many (or any) 40-foot sites.
If you do purchase that Vectra, suggest Sealtech to detect any recent rainwater leaks.
Full-timers, Fort Collins, Colorado
2005 Vectra KD, Jeep Wrangler