there is really no difference between AF and BA lounge and no sense for lounge hopping. I still try to find out which one is better, but cannot decide. Every time I try the other one than last time. One might suggest that the cake in the BA lounge in the afternoon is a plus, whereas in the morning you might find the AF breakfast offering more tasty, although both are not lounges where you want to spend more time than necessary.
If you want to hop into the other lounge use the mobile boarding pass which cannot be stamped.