The evaluation is based on your previous RV experience and what you have liked or disliked about other RV's you have been in. There is no "one size fits all" when it comes to anything about an RV.
We have had several different RV's, both gas and diesel. As our needs have changed, we either modify the existing coach, or buy a new one. We have gone larger and we have gone shorter, as our needs changed.
Right now we have a coach that suits us but next year we may decide we want something different.
Buy what you like and fits your needs now. No one knows what the future will bring.