I am not sure exactly what state Sierra is in but I have been in and out of Oakland over the last few months and their fleet looks smaller then when I attended.  Save yourself time and a whole lot of money, go to ATP.  I have been to both schools and I cannot tell you how many ex-Sierra people I ran into at ATP.  Unfortunately, they had already spent tens of thousands more then they needed to.  Check out the ATP forum.  Oh and by the way, this is not a shameless plug for ATP as I do not work for them, but I did have a fantastic flying experience there.  Best of luck.