Originally Posted by FBinNY

I consider this a "bird in the hand..." or "devil you know..." question.

If the existing bike components are working and doing what you want of them, you have zero to only little upside for improvement, so why even consider changing. OTOH- if the existing stuff is somehow - identifiably - lacking, then then there's little to lose, and rome for improvement, and a change might be warranted.

Once you reach mid level hardware, ie. Tiagra and up, the performance differences become very narrow, si it's about weight, cosmetics and prestige more than actually working better.