LSU's defense has been good, but not great like a lot of people have said so far this season. Statistically this season LSU's D has been in 6th or 7th place among SEC teams in yards allowed and in the mid-20s to mid-30s nationally (currently #24 nationally). They are good and definitely loaded with talent, but so far they have not been top 20 statistically.
On the flip side the LSU defense could be affected a little bit, at least in part, due to LSU's offense which has consistently been anywhere from 7th to 11th best in total yards gained among SEC teams (their current position is #11 after week 9) and ranked nationally anywhere from 70th to 87th in total yards (87th being their current position after week 9).
LSU is definitely Bama's toughest test so far this season, and I think playing at home LSU has a chance to win and could certainly cover. At the same time statistically Bama's offense is #2 nationally and Bama's defense has been improving lately and is now #16 nationally in yards allowed and #4 among the SEC teams. Statistically, Bama is the clear favorite this Saturday.