Can only compare F and intra-EU J class.


First:

Ground experience. If you are based in FRA vs LHR, Lufty completely obliterates BA. TKO round one first punch. From arriving at FCT until taking your seat in the plane you are treated to a flawless service. FCT dining service is on par with Michelin starred establishment. Food is of high quality and appears to be mostly prepared and cooked on site, unlike CCR. The private rooms/cabanas are three times the size of CCR/LHR and far more luxurious. Etro vanity products. FCT feels like quality and higher end, German built. CCR feels like designed by British, built with cost saving in mind by cheap labour.

Personal Assistant all they way through, Car to plane. The only upside BA have in the CCR are the wines. That is it. BA really should do some mystery shopping in the FCT and take notes.

There is IMO nothing First class about BA ground experience at LHR, except from the separated F check-in (manned by snarky staff) and once you are inside the CCR. A very nice lounge it is, but pales in comparison to FCL/FTL.

Cabin/Seat
In the nose of a jumbo 8 seats vs. 14.
BA:


LH:


For space LH wins without effort. For Privacy, even with the more cramped BA cabin I feel that due to the design of the seat BA still offers a more private feeling. Seat is less exposed.

Comfort: LH is bigger, wider and longer. Softer and superior in bed mode. However, the BA seat I find very comfortable for dining and lounging, and acceptable for sleeping. But it has a long way to go compared to LH.

Service: BA can be outstanding, mostly acceptable and sometimes terrible. We all know why. Crew of the day.
LH with my limited experience was good, but not stellar, even with moderately set expectation. A draw.

Food: no contest. And LH's food is not that exciting, it is just that BA's is rather underwhelming for being in First class.

Wine: no contest. BA offer more interesting choices, constantly.
LH ran out of premium Champagne on my recent sector. Only 1 bottle loaded!

Other: Bags of first. Always on LH. Hit and miss on BA.

To summarize: LH wins on all levels except for booze. It should be added however, if you are not FRA based, many of the FCT benefits are diminished.