I've not heard of the sissy sause. This has a little bite to it, and you can adjust the cayenne as needed. I grew up in Louisiana with REAL tabasco sauce, not the stuff I find on the grocery store shelves that has no heat in it.
Rudy's is good, but being in the Austin area I have access to much better, like Franklin's, Style Switch, all of the different Black's BBQ, Southside Market, Louie Mueller, etc.