LBs are overall a foot longer than SBs and that's divided into 6" longer in front of the rear axle and 6" longer behind it. note how fullsize trucks do not have the same equal split when going from SB to LB. they put the entirety of the extra bed in front of the rear axle.
honestly I don't think either distance will matter more than the fact that you're towing with a 30+ year old tiny soup can. meaning both wheelbases are equally good-ish.