The P+1 figures are interesting.

I'm in the middle of computing the B1 and B2 values for P+1 (to go along with the B1, B2 for P-1). 1/3 of the way so far.

Both methods provide the roughly the same number of factors (where p < 2^50) and the overlap (where a specific B1,B2 would have found a factor using either method) is relatively small.

(Sticking with B2=B1*100)

228541 factors < 2^50. B1=1000 B2=100000

P-1 finds 3516

P+1 finds 3423

BOTH: 44

229376 factors < 2^50. B1=40000 B2=4000000

P-1 finds 47113

p+1 finds 45112

BOTH: 9005

However, I'm having trouble with ecm 6.0.1 which I'm using for P+1. It segfaults in step 2 whenever I use an n > 1M. Will look into this further.

More stats later when I've factored all P+1's.