Benefits of Buying Used Equipment of Age

Hello Fellow Audiogoners,

My lack of ability to demo used equipment vs new equipment is bringing me to ask the following questions.

The following is an example:

Is it silly to buy 10 or 15 year old McIntosh (i.e. C41 and MC 7300 combo) vs brand new NAD (i.e. C165BEE C275BEE combo)

Silly meaning why buy something much older (yes one brand has benefits over the other on opinions I suppose) but from a design build and resolution, dynamic range?

What is the smarter purchase? Something that's been used for 10 or 15 years or something new.

I know it comes down to me but I am sure many people have this question because it was asked to me by a friend.

He said why would you spend 2k on a preamp that's 10 to 15 years old? And I said cause its McIntosh reputation etc etc, but he said SO haven't designs changed for the better? And I couldn't answer him party because to make a valid argument I would need to have lengthy experience with multiple products from multiple manufactures.

So I am reaching out to get some opinions about what would you do or better yet are the products of today better designed and you would trade older products for today's designs...