Pros depend on the program. Program's like Icahn's flex med let you skip the MCAT if admitted and you are guaranteed a spot at a really great medical school. Some might have an MCAT cutoff that isn't very difficult to clear (30 ish or even lower).
I cant answer the question on other schools knowing or not about your app to these programs but I can't imagine it would matter or that they would know. Since these programs dont use AMCAS (AFAIK) you wont show up as a re-app on AMCAS. Even so, these programs are crazy competitive most of the time so if you are rejected I doubt it would reflect badly on you. At most I could imagine someone seeing it and thinking "tried, but failed, oh well guess thats why he's applying traditionally now".
If a program wants you to score a 515+ and keep ur GPA above 3.8 I don't really see the benefits to early assurance unless you want to go to this school no matter what. The reason being that you might be shortchanging your potential options if you had just applied traditionally (including potential scholarships etc. once you are in that range of competitiveness).