I think it depends on your kid. If your kid is the type who likes all the "show and glory" then going on University Days is the better choice.
If your child is the type who wants a more "quiet and dignified" type of tour experience, then going on a regular day would be better.
Even if your child is not "into" college football (as my DS1 wasn't - he's the quiet, intellectual type), I must say that Bama is infectious. My DS1 is now very much into Bama football. LOL
That said, ALWAYS do a campus tour on a day that school is in session. No campus looks its best on a weekend. I think the best days to tour are M-Th. Fridays can be "mixed bag". If it's a home game weekend, then Fridays are too crowded. If it's not a home game weekend, then Fridays can also seem a bit less lively since many kids try to have few classes on Fridays. Both of my boys only have 1 class on Fridays.
If you've read my thread on UA Campus Tour Tips, you'll see that I also recommend taking the morning tour so that you can use the afternoon to visit to further explore the campus, speak w/ profs, or "sit in" a class (arrange thru department ahead of time).
When will you be touring?