Believe DTW is still the 763 on this route while JFK and ATL are both A330s which are significantly better. The downside IMO is JFKLHR is way too short if you are looking for an experience and a decent sleep though you get Clubhouse access which is nice.

If having the experience onboard is the goal I'd route via ATL for maximum A330 time.

That said if doing award tickets I would take the cheapest D1 option since it's a relatively short flight over spending additional miles for a specific routing (unless you have unlimited miles).