Now I do know that obfuscation is never 100% safe, but it's better than nothing when attempting to avoid others from decompiling your .swf files.
I googled and found one which only changed variable names and removed comments. I need something more advanced. Any recommendations?
It seems you use Flex, so if you use a lot of MXML, than there is no need for obfuscation. It is hard to reverse engineer the original MXML from the decompiled ActionScript that has been generated from that very MXML source. The generated ActionScript is not really a pleasure to work with.
Why it is so vital to prevent others from decompiling your swfs? Comments always get lost during compilation and local variables/function parameters lose their names. If your code is so revolutionary and complex that people rely on decompilation to reverse engineer it, than this fact will make it very hard for them. Most of the time trying to reimplement things is cheaper. In the end, I think decompiling SWFs is as pointless as obfuscating them.
For that reason, I don't really know any obfuscators. The only good ones I knew for AS2 increased filesize by more than 100% and slowed down performance critical parts drastically which in my eyes decreased the value of the application a lot. A price I wouldn't pay for code security. I also don't mind sharing my code, but that's a matter of philosophy.
You should instead focus on creating an outstanding software and placing it well on the market. Be it obfuscated or not, there are always people capable of reverse engineering it. Getting a good market share and simply have a very high quality are things that'll guarantee success of your software, disregarding copycats you might even wan to open source big chunks of it, since this is a further discouragement for commercial competitors, and non-commercial ones will never try to kick you out of business, plus they may even give useful input.
I would not say I could vouch for this, but I see them on almost every flex blog I go to: secureSWF
Here is also one of the most popular actionscript obfuscators. Pretty reliable and the price is affordable.