We have been to tons of Creation events, including the one in San Francisco in November.
The Summit will be bigger, with non-Trek actors there. I understand the TNG cast is going to appear together onstage during that event.
The San Francisco one will probably (I don't know for sure) be just Star Trek, and since we already had our TNG Anniversary con last year, I imagine it would be actors from many different series. The guest lists on these things can change up to the last minute.
Creation Cons are very good, and very bad. They are good in the sense that they are professional and pretty well organized. You have a lot of different options as to the experience you want to have: seating, autographs, photo ops, etc. and a lot of different pricing options.
They do, at times, have an assembly-line feel to them. Things seem rushed, and impersonal. Most actors are great, a few don't even acknowledge you are there. A Creation Con is like going to a restaurant that serves really good food, but every course costs something extra, and so do the cups, knives, forks, etc.
Still, if you have the money to spend, you get a pretty cool experience and hopefully a few nice souvenirs.