New or Old

I wouldn't risk the KEFs. I get the feeling you wouldn't either and are looking for confirmation here. 

assume you are talking about this JBL sale

https://www.jbl.com/loudspeakers/STUDIO+590.html

You can pass on both, keep looking, but for around $500. a bit more for the KEF, either is a lot of speaker

perhaps stop, ask yourself, are you looking for a great deal or a great sound? New with warranty, or risk?

Only return shipping involved with the JBL’s, audition IN YOUR SPACE, I bet you more than likely will keep them. At that price, you could listen to them for a few years, sell them, move on.

Assume either would be darn good: WAF, is there any wife acceptance factor involved? Which speaker do you want to look at every day for years?

Hi Elliot, yeah that is the sale, $1100 for a pair delivered. KEFs are $1300, with another pair at $1800 for sale a little further away.
I am of course looking for a great deal and a great sound.
WAF is covered, she would prefer the all black of the JBL, but will tolerate the rosewood KEFs (especially if I let her wrap them in black cloth or vinyl), so no issues there. 
Can locate them 6-12 inches from wall, so maybe KEF would be better that close.

I think I am looking for someone to say something definitive - the KEFs are ruined because the foam is not the original, or the KEFs are reference speakers and would be $10k in today's dollars and are leagues ahead of $2k new speakers (and considering the JBLs go on sale like this once a year, are the really just $1k speakers anyway?) or that the JBLs are miles better due to new tech and design and materials, and are warrantied for 5 years, and the KEFs could fail any day now and not be repairable.
Stupid pandemic, I want to be out touring places and auditioning speakers.

I guess the JBLs seem the safer bet, as you say, a few years then move on to something else.
But will I always be wondering how good the KEFs really are?.

Noromance:- maybe, but I also love a bargain and getting $4k speakers (1985 prices) for $1300 could be a bargain, or could be a money pit. It really is a question of which will sound best in my home, and it seems the chance to audition both there is not going to be practical.

So many choices, so many hard decisions.

The KEF 107 is a fantastic speaker and hard to beat if everything is working properly. The Kube is essential with them if you want the full bass response. The T33 tweeter will probably need the ferrofluid replaced. It was an easy job on my 104/2s and only took about 30 minutes for each tweeter. The B110 midrange driver should not require anything. If the woofers have been reformed than they should be fine. The only other thing is the caps in the crossovers. They may need replacing. However, I have found the caps typically to be ok in this generation of speakers. 

any kef woofers from that period will have the surrounds replaced. I sold my pair for $1050. They were the R107/2 and the kube was included with grills. They were listed months with very little interest as those who like them wait to ‘score’ a pair. $800. Tops since they’re 30 years old.