I find it hard to believe that the BA lists are more diverse than the IG. I would not be surprised if the BA where all variations on razorback spam.

Guard on the other hand have
-infantry (no mech) - which cheese (if I am not mistaken) feels is the stronger list
-mech guard - which is the strongest in my area
-a mix - this will have the biggest variation and I would not be surprised if these place because the vehicles are so good and the units are so cheep that there is a lot of customization.

that is 3 variants each which are competitive (the first two more so than the last but it is possible with a good general or some odd strategies)

while BA have the one (razor spam)