American cons are just mind-blowing, you're in for an incredible time

We've never made it to Comic-Con ourselves (we've booked in for our 4th Dragon*Con next year though), but tips we've picked up from friends that attend SDCC -
- the tickets sell out incredibly fast (last year, the website kept crashing, many people missed out on badges). They have a capped attendance number, so it's very competitive.
- the official hotels seem to run on a lottery system - you pick your top choices, then they email out with what hotel you were assigned (they book out the surrounding hotels, so if booking outside the system, you'll probably be further way from the con).
- the big name panels in Hall H will take several hours of lining up (4-6 hours is not unheard of). If there's a panel you don't want to miss, plan ahead.
- Preview night used to be the best way to see toy/collectible releases, but it's now just as busy/popular as the main 4 days.
When we book our Dragon*Con hotel, we need to be online before the stated time, refreshing constantly with multiple people accessing the site. These websites almost always overload, and it's a matter of determination and perserverance to get through - selling out in 4 minutes is common for D*C. SDCC is a bigger convention, so there's more people all fighting for tickets and hotels, it's very competitive - sign up for all the alerts to make sure you don't miss the day/time things go on sale.
Personally, D*C is our preference, from a costuming and socialising point of view

We'd love to make it to SDCC, but we have so many friends at D*C, we just keep going back.