Personally i had to learn my fitment and bike preference the expensive way. I had some tips over time from dealers, fitters etc.
But i think i have stems in rows, several bars, saddles aso. I always measured alot to understand, discussed with different builders on what affects the feel of the bike in terms of fit, layups and tubes shapes. It is quite funny but very expensive. I find many bike stores/ dealers have a narrow window of knowledge and/ or often knowledge around the products they carry. Better keep to facts as subjective things is hard to rely on.
All in all i deem comfort and fit highest. If bad fit or painful(bad comfort), i find that it's tougher to develop.
When we try new bikes, it's quite easy to fall in love with new aspects. Question is if it is just "the new" which is a nice feature or experience, or if it is a step up in long term.
Around here we have no super long hills or descents, it's quite windy and often it feels like side and swirl winds.
I have a few buddies i use to discuss with. What i find funny is that most of them only rely on sales talk and sales propaganda.
I think manufacturers test is best done with a third part company. Like stiffness to weight and technical benefits in compairson to other similar products/ brands. When we see inhouse tests showing that brand A is better than brand B and C, and brands B has a similar test it's a bit fishy.
An open mind is always good to have.